6. Aegoeonichthys appelii Clarke.
To Mr. A. Hamilton, Director of the Dominion Museum, Wellington, I owe the privilege of examining the remains of a specimen of this species. This specimen is, I believe, only the second known; it is in rather deplorable condition, being in two pieces, and has been otherwise so cut about that no fully satisfactory description can be made. Mr. Hamilton writes, “Please do whatever you like with the skin; it is so torn and knocked about that you will find description a difficult matter. The specimen was caught by some fishermen on a line at the Heads (Port Nicholson), and used by them for bait. Somebody saw it in the boat, and brought the remains to me.”
Though the specimen is in a very dilapidated condition, the rarity of the species makes it advisable to attempt to extract some few grains of information from the remains, and these will be useful in the case of definite and fixed characters.
The type specimen was described and figured as having the head and body strongly depressed, and as the author had the specimen entire, and probably unmutilated, his description may be correct; judging from our remains alone, I should have said that the head, body, and tail were all compressed, but the jaws appear to be so extensible and dilatable that the contour of the head may perhaps be altered with the varying positions of the jaws. Respecting this subject, Günther* writes, “According to the figure, Aegoeonichthys would appear to be much more depressed in shape than Himantolophus; however, we must remember that these flaccid deep-sea fishes may assume, or be made to assume, very different appearances.”
By careful piecing together it is found that the whole of the skin of one side and of portion of the other remains, so that it is possible to correctly render an account of all the fins, and the number and disposition of the dermal scutes. The whole of the body, with the exception of the vertebrae, is missing; but if all the vertebrae are represented, as I believe they are, their total number is 17, and this is also the number supplied for Halieutaea, another member of the order.
Of Aegoeonichthys Günther also writes, “Unfortunately, nothing is known of the gills of this fish, which, as regards grotesqueness of form, surpasses the fishes of the preceding genus (Himantolophus). It is evidently closely allied to Himantolophus reinhardtii, and I therefore suppose that it possesses the same number of gills. If this should prove to be the case, the question will arise whether it should be kept as the type of a distinct genus.”
[Footnote] * Gunther, “Challenger Reports,” vol. 22, 1887, p. 51.
The gills in the present example are, fortunately, preserved, but as I cannot refer to Lütken's paper* in which Himantolophus reinhardtii was described and figured, I am not in a position to decide the question as to generic identity. It is, however, possible that with the aid of the following description others more fortunately situated may be able to do so.
The figure published in illustration of Clarke's paper† is somewhat crude, and, gauged by the characters of our example, incorrect as regards the cephalic tentacle and the number and disposition of the dermal scutes. I have therefore thought fit to refigure the species from the assembled remains of the specimen intrusted to me. I have also essayed a description of the specimen, but owing to the imperfect condition it will be understood that the proportional measurements are merely approximate, or, it may be, even conjectural. These remarks apply, however, only to the relative width and depth of the body and head, the bones being so flexible that the character of the head may be made to assume either depressed or compressed condition, while, as before stated, the absence of the soft portions of the body renders its original shape largely conjectural.
D. I, 5; A. 4; V. O; P. 17; C. 9; Vert. ? 17.
Head enormous and grotesque, its length half that of the total, computed from the tip of the snout to the base of the caudal fin; its depth is one-fifth greater than its length, and its width is a little more than half its length. The cheeks are subvertical, and the eye is placed in a large shallow depression rather high in the head. The eye is very small, about 12.3 in the head; it lies midway between the tip of the snout and the supraorbital spine; the latter marks the termination of the supraoccipital ridge; this is widely separated from its fellow where it originates behind the premaxilla; these ridges diverge behind, but are somewhat contracted in the middle. The interorbital space is deeply concave, and from its centre the remarkable tentacle takes its origin.
The gape is very wide, and the mandibular articulation is in advance of the eye, and even in front of the tip of the snout. When closed the mouth is almost vertical.
Teeth.—The teeth are in about three irregular rows, the innermost containing the largest; they are spine-like, slightly recurved, and depressible; they are slightly longer in the lower than in the upper jaw; the longest are one-fifth more than the diameter of the eye. There are no teeth on the vomer or palatines. Upper pharangeal teeth only are present; they form two clusters, which appear to act in apposition, the teeth of each group being directed towards each other to form a grasping apparatus. The teeth are similar to those in the jaws, but shorter and stouter, their combined number being 14. There are no teeth on the lower pharangeals.
The chin forms the anterior contour of the head, projecting far beyond the mouth when it is closed. There is an extensive frenum behind the teeth in both jaws.
The branchiostegals are 6 in number on each side; they do not bear teeth, as stated by Clarke, who possibly wished to express the character of the branchial arches. The gill-opening is small, and placed below the base of the pectoral fin. The gills may perhaps be denoted by the formula applied to Himantolophus—namely, ½2½ pairs—but a more detailed account of their character will be advisable,
[Footnote] * Lutken, K. dansk. Vidensk. Skriv., 1880, p. 309, pl. 1, 2.
[Footnote] † Clarke, Trans. N.Z. Inst., vol. 10, 1878, p. 245, pl. 6.
The outer branchial is free only in its posterior half, the anterior portion being adnate to the ceratohyal. This attached portion only bears gills: they are much smaller than those of the other arches, on which they are of considerable length. There is no trace of paired arrangement in the gills of this outer arch. A paired disposition is apparent in the gills of the two middle arches, for, though the rays are set in continuous series, they are of heteracanth nature. The inner arch is wholly adnate to the membranes at the lower part of the tongue, and is fully furnished with gill-rays. The gill-rakers are spiny tubercles; there are 12 on the first arch, one of which is on the upper limb, just above the angle; the rakers on the median arches are in two rows, arranged alternately, there being 19 on the second arch.
Fins.—Some idea of the character of the dorsal tentacle will be derived from Clarke's figures, but as it was evidently imperfect. and is even more complicated than drawn and described, the following description will not be out of place:—
The tentacle lies in a deep groove between the supraorbital ridges, its bulbous base being rather nearer to the mouth than is the eye; the shaft is very stout, and it terminates above in a large semispherical bulb, its total length from base to summit being 1.7 in the length of the head. From a cup in the summit of the bulb arises a freely movable stout tentacle, which divides at a short distance above its insertion, each branch throwing off 2 smaller twigs at about half its height. Inserted in the bulb and behind the cup are 2 thick branches, which, however, arise from a common base: they become flattened distally, and each, after throwing off a twig from its inner side, divides into 3 arms; these are again subdivided, but the divisions are not the same in the two branches The illustration accurately depicts the condition. Also, on the hinder part of the bulb, but nearer its base and sides, are two other small twigs. The word “frond” would perhaps be more appropriate, for the whole tentacle may be likened to a plant of Fucus, the so-named twigs being quite like the fronds of a seaweed, while the main and secondary stalks answer to the stem and branches of the plant. There are, in all, 20 terminal fronds, and the distal portion of each is nacreous white, and is no doubt luminous in life. When the tentacle is bent forwards these luminous tips dangle just in front of the mouth, and are no doubt very effective lures. It will be apparent that the tentacle was incomplete in the type specimen, the stalk arising from the middle of the cup being absent, and doubtless leading its author to conclude that the substance within the cup was luminous, though he does not actually say so.
The dorsal fin has a slightly more forward insertion than the anal, and has one more ray. The first is simple, the other four being divided nearly to their bases. The third is the longest, being 3-2 in the head. The last ray is connected to the peduncle, just free of the upper caudal ray. The anal is very similar, but the first two of its 4 rays are simple. The pectoral is short and rounded, and is placed nearly midway between the end of the snout and the base of the caudal rays. The caudal is large and rounded, arising from a very compressed and short peduncle, whose depth is equal to the longest dorsal ray.
Armour.—The skin is soft and loose, warty on snout and chin, and, excepting the top of the head, cheeks, lower jaw, and all parts in front thereof, studded with round cartilaginous scutes, each of which bears in its centre a hard low thorn with roots radiating into the body of the scute.
Some of the scutes are much larger than others, and their exact number and disposition are shown in the illustration. The covering of the main stalk of the tentacle is formed of a mosaic of very small scutes, which also bear spines, but they are reduced to hard tubercles.
Colours.—After long immersion in preservative the general colour is a pale-flesh tint; the margin of the jaws, the post-dental frenum, the space around the eyes, and the wart-like elevation on the chin are brown; the mid-line of the back and part of the stalk of the tentacle are also brown: the branches of the tentacle are black, but their tips are white.
Some Measurements.—Extreme length, chin to end of caudal, 410 mm.: length as basis for comparisons, 270 mm.; length of head to gill-opening, 135 mm.; diameter of eye, 10 mm.; length of tentacle-stalk, 78 mm.; extreme length of tentacle, inclusive, 205 mm.