Art. VII.—On a species of Ophisurus, found on the Coast of New Zealand.
[Read before the Wellington Philosophical Society, August 14, 1869.]
The genus Ophisurus includes a section of the Eel family, which has not been previously recognized as represented by any fish on the New Zealand coast. The only eels mentioned in the lists of New Zealand fishes, are two fresh water species, Anguilla Australis (also found in Australia), and Anguilla Dieffenbachii, which Richardson considers as only a variety of the former, and a Conger Eel (Congus habenatus), which is found in Cook's Strait, and on other parts of the coast.
In Richardson's work “On the Antarctic Fishes,” he describes twenty-five species of Ophisurus, but they all appear to have been obtained from tropical seas, and none of them present the same characters as the fish which I have to describe.
The specimen was received, with the following memoranda, from Mr. Atkinson, R. M.—“Puni Horua, caught in a tidal creek, near Makaraka, Poverty Bay, June 24, 1869.”
The form and colour of the specimen has been considerably altered by the spirit in which it had been preserved, but it presents the distinctive characteristics of the Ophisurus, or Snake-Eels, having the slender, compressed head, and slightly expanded snout, and the tail prolonged to a naked point, beyond the dorsal and anal fins. Its colour is dark chesnut-brown, with a silvery lustre beneath. The nasal disk is bordered by six acute subulate teeth, and on the mesial line, two minute teeth, and one stout acute tooth. Behind this, the vomerine teeth form a single row in the mesial line, commencing with two stout teeth, and continued by twelve minute, recurved, subulate teeth. Palatine teeth are uniserial, consisting of thirty-four minute teeth, with recurved tips, extending from the nasal disk to the angle of the mouth. The mandibular teeth are uniserial, and correspond, in number and form, to those on the nasal disk, and palatines. The eyes are placed in the middle of the gape, about half the diameter of the orbit below the top of the head. The gill openings are large, and placed in front of the pectoral fin, which is small and acute. The dorsal commences over the pectorals, and lies in a groove extending to within half an inch of the tip of the tail; its greatest height being three lines. The anal extends to within three lines of the tip of the tail, and is four lines wide, immediately behind the anus. The total-length of the fish is thirty-four inches; tip of nose to anus, thirteen inches; to gill openings, two inches six lines; length of gape, one inch four lines. The nearest species described by Richardson is O. Eostellatus,* from Senegal, but it presents marked differences in the dentition, having a different number of teeth, which are biserial; and in the pectoral fins, which, in O. Rostellatus, are large and oval. The proportions are also slightly different. I therefore propose to distinguish this fish as a new species, and call it Ophisurus Novoe Zelandioe.
[Footnote] * Richardson's “Antarctic Fishes,” p. 105
Dr. Knox having undertaken the dissection, and minute anatomical description of the specimen, has furnished the following valuable notes; together with the preparations they refer to, which are deposited in the Colonial Museum.
Anatomical Observations on Ophisurus Novæ Zelandiæ, (Hector.) By Dr. Knox.
The external characters of this fish having been given by Dr. Hector, I shall only make a few remarks on the skin. The specimen having been preserved in strong alcoholic mixture, necessarily altered, not only the colouring, but also the integumentary tissue itself; not a vestige of scales could be observed, and considerable difficulty was found in removing the skin, more especially at the connection of the dorsal and anal fins. Little or no oil appeared to be present, and when dried, the absence of oil became more striking. I found it, viewed as a transparent object, entirely dotted over with minute black spots; and immediately below the lateral line, a regular series of spots of larger size, and placed at about two lines from each other. These latter I consider glandular orifices; they are also very distinct on the lip or margin of the upper and lower jaws. On the inner surface of the abdominal aspect of the skin, there extends, from the gill aperture to the anus, a well-developed cutis-muscle, which, by its contraction, will assist in progression, in a similar manner, to the abdominal scutœ in some of the Reptiliae (Tuatara, etc.), no doubt required, in consequence of the extremely rudimentary nature of the ribs.
The Skull—Fig. 4.
The head of the Ophisurus is at once remarkable for its smallness, and for its high degree of development. The organs of sense, and the dentition, are fully represented. The Ophisurus stands, in this respect, in strong contrast to fishes, in which the head is almost universally, enormously (disproportionally) developed. Even in his closely-allied relation, the eel (Murœna, Linn.), the head continues to hold something like a proportion to the body. It will be seen from the annexed table of weights, that the total weight of the skull is thirty grains, but this is much beyond the true weight of the bones, as the integumentary covering on the right side, was left in sitû, in order to display the position of the nostrils, and the gill coverings, and thus the bones in the skeleton of the head would certainly not weigh more than fifteen or twenty grains.
The smallness, added to the non-development of the osseous centres of ossification, render any attempt to describe the separate bones of the skull, impossible. The view of the skull from above (Fig. 5) exhibits, very beautifully, the fact (although not very long ago, the theory) of the head being merely a continuation of specialized vertebræ; it does not signify whether the number be 3, 7, or 7 times 7.
The upper jaw (Fig. 6), after gradually narrowing, expands into a semi-oval surface, convex above, concave on its dentar or buccal aspect. The rami of the lower jaw (Fig. 7) are proportionally long, and quite straight, terminating with a symphysis peculiarly formed, so as to receive an azygos tooth in the upper jaw. The opercula are well developed.
The lower jaw (Fig. 7) is formed of two perfectly straight rami, uniting at the symphysis by cartilage, and articulating with the articular process of the temporal bones in the usual manner; the temporal fossæ are large, affording ample space for the attachment of strong temporal muscles, no doubt occasionally required when an unusually large crawfish is selected for a feed.
The dentition of the Ophisurus differs so entirely from that of the eel, as to remove it from the same class or order of fishes, but it would be a great stretch of classification to place him with the serpent, on account of his peculiar dentition. The teeth are all conical, but vary in size, evidently suited for seizing, killing, and retaining the prey. I conclude that the food will consist of crustaceous insects of considerable size, which will be swallowed entire, to be acted upon by the juices from the inner surface of the capacious stomach. On the alveolar (dentary) margin of the upper jaw, and on the expanded extremity (Fig. 6) there are seven teeth, an azygos tooth, and three on each side, which gradually increase in size as they leave the mesial line; a vacant space corresponding to the contraction of the jaw, above alluded to, is followed by a series of minute teeth. On the mesial line of the jaw, a peculiar arrangement occurs, in a line with the azygos tooth, one a little larger follows, then two minute teeth, then a tooth still larger than the first, followed by an empty space, then a tooth still larger than its predecessors, and then an empty space, then a tooth less than its predecessor, which is followed at a little distance by a smaller one, and a series of minute teeth follow, becoming gradually microscopic. The entire mesial series, above described, are embedded in a groove, occupying the entire length of the base of the skull, and approaching closely to the first vertebra of the spine. The transcendental anatomist would call these teeth vomerine, but I shall continue to look for the vomer, in connection with, and performing its usual function, as dividing the nostrils.
The lower jaw (Fig. 7) supports three teeth on each side, corresponding to those on the upper jaw, and leaving a space at the symphysis for the azygos tooth.
The alveolar (dentary) edge then supports a series of minute teeth of beautiful regularity, resembling a fine saw, or comb.
The tongue is edentulous, but the pharyngeal bones are covered with minute teeth; a series of a slightly increased size, bordering the external margins of these bones. The arrangement, no doubt, when brought together by the action of the pharyngeal muscles, in performing the act of swallowing, subjecting the shrimp to a severe scrutiny, not only touching its quality, but its vitality.
The Vertebral Column.
In order to facilitate description, and avoid repetition of terms, I propose to describe the Ophisurus as presenting a dorsal and abdominal margin, and right and left lateral surface, as being equally applicable to the skeleton, as to the external surface of the body. The osseous tissue approaches that familiar to the anatomist as the semicartilaginous, although each individual vertebra is well defined by a perfectly formed articulation; and the canal for the spinal marrow is composed of a texture more resembling the shell, in hardness, than bone. In viewing a separate vertebra (Fig. 3a), the spinal canal will be observed nearly as large as the articular surface of the body of the vertebra, and the proportions still continued throughout the entire spine. A mere rudiment of the spinous process exists, and a fibrous membrane of considerable extent separates the interspinous processes and fins, from the vertebræ. On the abdominal line (Fig. 3b) on each side, a plate, or process, extends, and presenting a convex free margin to which is articulated an exceedingly delicate rib, the ribs, indeed, more resemble a fine hair than a bone, and do not admit of drying so as to be seen in the skeleton.
Fig. 3c is a lateral view of three of the vertebræ, and exhibits the rudimentary state of the spinous processes, and the fibrous membrane separating
the inter-spinous processes, and corresponding dorsal fin, from any immediate connection with the spinous processes of the skeleton, explaining the almost complete disappearance of the fin, in the recently caught specimen. The abdominal plate or process will be observed to support the ribs, as previously remarked; and it is necessary, particularly, to refer to this fact, as, in describing the caudal division of the spine, it will be again alluded to.
About the eightieth vertebra, the canal for the blood-vessels begins to be formed, and here an additional system of processes is found. The abdominal processes close upon each other, still continuing to support delicate, hair-like, ribs, while a series of cartilaginous processes gradually appear on the lateral surfaces of the bodies of the vertebreae, and continue to the extremity of the spine. There are two of these processes on each side, evidently arising from the vertebræ in the fish being composed of two elementary parts, divided transversely in the middle, like an hour-glass; and the resemblance is rendered perfect by the communication being free, a fine wire passing readily through. The fact of a vertebra being, at an early period of the progressive development of the skeleton, composed of the elements of two vertebræ (and this can scarcely be doubted), would, if the development was arrested, give double the number of vertebræ, or 420 instead of 210.
Had Sir Charles Bell selected, for his Bridgewater Treatise, a vertebra, instead of the hand, as illustrating the “Unity in the Type of Organization,” he would undoubtedly have experienced much greater difficulty in producing a very popular volume, for which he received the very handsome sum of £1000. The treatise, it would appear, gave offence to no one, and, yet, it was a very bold proceeding to trace analogy between the boasted hand of man, the club shaped pectoral extremity of the elephant, the bat's flying arm, and the fin of a fish.
I have remarked, are exceedingly delicate, and more resemble numerous, hair-like, semi-ossified, prolongations, giving attachment to the intercostal muscles. In many species of fishes, as, for example, in the herring, these same ossified processes are very numerous; and, I think, by many anatomists, are considered ossified tendons of the muscles, not found in any other animals but fishes. In birds, we observe a tendency in tendinous prolongations of the muscles to become osseous, but these ossified tendons in birds, cannot be considered in any way analogous to the hair-like processes I now allude to.
The Locomotive Organs
in the shape of the pectoral and ventral fins, are not particularly well represented. No vestige of ventrals can be observed, and the pectorals are exceedingly small. The Ophisurus finds his food amongst the mud and stones, in the estuaries of rivers; and with the assistance of the cutis-muscle, already alluded to, will be able to make considerable way over the mud. I may remark, that the Muroena, or common eel, does not possess this abdominal cutis-muscle, but a thin layer of muscular fibres can be observed on each side of the caudal extremity, acting in a lateral movement of the tail, and facilitating the eel in progressing through the water.
The Muscular System,
it will be observed, from the annexed table of weights, is greatly developed, and altogether connected with the spinal column—the pectoral fins being merely rudimentary, and the ventrals entirely wanting. A careful anatomical dissection would, no doubt, show that the anatomy of the human subject, was not essentially deviated from. It may suffice, however, to state, that it
consisted of four bundles, two on each side, divided by a fibrous aponcurosis, and numerous fine, hair-like bones attached, especially in the situation of the lateral line, and also to the skeleton. In treating of the skin, I have alluded to the cutis-muscles extending from the pharynx to the anus, as, no doubt, supplying the want of the usual pectorals and ventrals. In describing the skeleton, I have mentioned the development of lateral processes in the caudal portion of the spine, those processes were closely attached to the spinal muscles, and the great vascularity of the muscular fibre, indicated the constant use, and great power in all the lateral movements of the caudal extremity.
Organs of Sense.—Smell.
The nostrils opened on each side of the upper jaw, about half way from the tip of the jaw to the centre of the eye. They present a kind of representation of the aloe in the human subject, and, no doubt, could be closed, or opened, according to circumstances; and, indeed, I observed on the inner surface of the integuments, in the situation of the nostril, a series of fine semi-cartilaginous fibres sweeping around the situation of the nostril, resembling the radii supporting the membrane surrounding the gills: a bristle introduced into the nostrils, passed directly into the cavity lodging the brain.
The eyes are protected (I cannot say concealed) by the integuments passing completely over the orbits, having no connection similar to a tunica conjunctiva, with the eye itself. The detached skin, however, when dried, exhibits a beautiful transparency, answering the purposes of a pane of glass, and protecting the eyeball, under all circumstances.
The single specimen I had, afforded no means of ascertaining the power of hearing, or state of the ossiculæ.
Circulation, and Organs of Respiration. (Fig. 8.)
The heart, remarkably small, but formed of an auricle, ventricle, arterial bull, and brachial artery, as in other fishes.
The tongue is edentulus.
Hyoid and Branchial apparatus so perfectly accord in the Ophisurus, with the type observed in fishes, as to leave no doubt as to what division of the vertebrata it belongs. The chief difference from that in other fishes, is in the Radii Branchiostegi, and in the extreme smallness of the Hyoid bones. The Radii of the Ophisurus (twelve on each side) are grouped in close juxtaposition, at their attachment to the hyoid, but, branching out, make a sweep round the operculum, nearly meeting on the dorsal line, and being intimately connected with the integuments, might escape the observation of the naturalist. The free margin of the branchiostegal membrane forms the anterior edge of the gill apertures, whilst the pectoral fins form, in a great measure, the posterior margin, evidently assisting the radii, branchiostegi, and membrane, in guarding and adjusting the all-important gill openings. The branchiæ appear to have been composed of little tufts. The state of the viscera prevented me from ascertaining the presence, or absence, of a swimming bladder.
Organs of Digestion (Assimilating).
The Œsophagus is wide, and composed of three tunics; the muscular layer of great strength; the inner or mucous membrane, resembling the lining
membrane of the gizzard in birds, is raised into eight longitudinal folds. A finer arrangement of the longitudinal folds marks distinctly the commencement of the stomach, which terminates in a sharp point. The pyloric valve is placed about the centre of the stomach, and presents a complete obstruction to any thing passing to the intestine, independently of the vital phenomina. The duodenum, and the remainder of the intestinal tube is distended, but gradually contracts, and becomes nearly straight.
The duodenum, when divided longitudinally, exhibited a finely reticulated, honey-comb surface. No vestige of pancreatic cœca could be detected.
The liver, square-shaped, lay imbedded, as it were, between the oesophagus and intestine; it was of a pale brownish-yellow colour, soft and friable.
The kidneys, in position and structure, resembled those in the anatomy of the Murœna.
No organic remains could be detected in the stomach, or intestinal tube, and the utter absence of any fatty deposit was sufficiently curious; perhaps the specimen had just emerged from its winter quarters in the mud.
resemble those of the eel, and being in their minimum state of development, or season, some difficulty occurred in even determining the sex.
|Snout to tip of tail||2||11||0|
|" nostrils||0||0||4 ½|
|" centre of eye||0||0||10|
|" angle of mouth||0||1||4|
|" free margin of operculum||0||2||6|
|Greatest circumference—centre of body||0||3||6|
|Tip of tongue to pyloric valve||0||5||0|
|Pyloric valve to extremity of stomach||0||4||6|
|Plyroic valve to anus||0||10||0|
|Weight of entire specimen before dissection||0||8||0|
|Weight of head||30 grains|
|" tongue and branchial apparatus||10 "|
|" spine, etc.||370 "|
|Total Weight||410 grains|
|Weight of recent entire specimen||0||8||0|
|Deduct weight of skeleton||0||0||410|
|Deduct weight of skin, 180 grains||0||1||20|
|" viscera 320 "|
|Weight of the muscles||0||6||50|
|Weight of single vertebra (the 80th being the largest) 1 grain.|
|Note. —Number of Vertebræ determined by Dr. Knox:|