on the arch of the atlas. Parotic processes (pterotic [ unclear: ] opisthotic) are not present in their typical form, the post-temporal being interposed between these two, and so closely applied as to simulate a cranial bone; but the opisthotic has a short process, between which and the post-temporal there is a pit for articulation with the supra-clavicle. The lateral border of the pterotic forms eaves overhanging the hyomandibular articulation, the surface for which may be traced forward from the pterotic to a pit between the prootic and sphenotic.

The lower posterior angle of the cranial cavity is a cartilage-lined pit, formed mainly by the opisthotic, between the exoccipital and the pterotic, and overhung by the epiotic; it receives the lower end of the posterior semicircular canal which pierces the large epiotic. This bone and its fellow form the upper third of the posterior cranial wall and part of the roof, on both of which they meet by a median suture. The square prootic has its mesial border split longitudinally to form the roof and side-walls of the subcranial cavity for the ocular muscles. This cavity is closed in below by the parasphenoid, and extends back into the basioccipital; the prootics meet behind above this cavity, but in front are separated by the very small prepituitary Y- or rather T-shaped basisphenoid whose slender stem extends downwards between two processes of the parasphenoid. There is no alisphenoid bone; and the sphenotic entering into the posterior orbital boundary is almost covered by a lateral-line bone. The frontals are strong curved bones above the orbits, their anterior points flanked by the parethmoids between the orbits and the nasal cavities. The nasal cavities, separated by the supra-ethmoid and the underlying cartilage, communicate with the orbits by foramina between the parethmoids and the median cartilage. Dorsally, between the slender nasals and (between) the lachrymals, above the thin supra- or dermo-ethmoid, there is a long median space in which slide the nasal processes of the premaxillæ. The vomer consists of a slender ventral process and two short stout dorsal processes, and embraces the anterior end of the median prenasal cartilage. The lateral or suborbital chain is represented by five bones: first, the large, slightly mobile, fenestrated lachrymals; second, a small bone on the inferior border of the parethmoid; third, a long bone forming the inferior orbital boundary, having its lower posterior angle movably connected with the anterior border of the preopercular; fourth, a thin plate on the sphenotic; fifth, a nodular bone in a space between the parietal, pterotic, and post-temporal.

2. The Jaws and Suspensorium.—The short jaws are carried, with the lower end of the hyomandibular, far forward from beneath the cranium; and the rodlike symplectic, meta

pterygoid, and quadrate are nearly horizontal. The pterygopalatine region is imperfectly ossified, and there is no separate mesopterygoid. On the upper angle of the quadrate is perched a small ossification—“pterygo-palatine”—which is carried so far forward as to lose the typical articulation with the parethmoid. The hyomandibular is a stout plate, with a posterior process bearing the opercular. The premaxilla consists of a short alveolar plate, and a long semi-cylindrical nasal process bound immovably to its fellow of the opposite side. The maxilla does not enter into the gape: it has two mesial processes connected with their fellows of the opposite side respectively above and below the combined nasal processes of the premaxillæ; and the bone rotates around the lower process. In the lower jaw, the dentary forms a short V, with its broad apex (anterior) joined to its fellow of the opposite side by fibrous tissue; hence the posterior extremities of the rami can be approximated. The articular bears a saddle-shaped facet for the quadrate, and its anterior part projects as a lamina into a cavity in the dentary. Meckel's cartilage can be traced forward on the inner surface of the articular as far as this cavity. The articular bears on its base and inner surface a nodular angular connected by a strong ligament with the interopercular.

When the mouth opens, the dorsal angle of the dentary is rotated forward, carrying with it the premaxilla, whose nasal process, with its fellow, slides in the naso-prenasal groove. These processes are connected by soft tissue with the walls of the olfactory sacs; and by their movements produce an ebb and flow of the contents of the sacs.

3. The Operculum.—The pre- and inter-operculars are prolonged forwards like the suspensoria, and almost reach the articular head of the quadrate. The preopercular alone has a roughened skin-surface. The fan-shaped opercular is very mobile on the process of the hyomandibular, and it and the preopercular respectively hide the larger parts of the weak subopercular and the bladelike interopercular. The preopercular covers the posterior border of the hyomandibular, but not the symplectic; and receives the border of the quadrate into a groove on its upper border.

4. Hyoid Apparatus.—The short cornua are suspended by small interhyals from cartilage between the symplectic and the hyomandibular. All the ossifications are small; and the epi- and cerato-hyals bear equally between them the five thin branchiostegal rays. The couple of hypohyals are separated from those of the other side by two small bony nodules and by the head of the spatular urohyal.

5. Branchial Apparatus.—The very short branchial arches together form a very compact mass perforated by the pharynx,

and containing thirty-four ossifications. The first arch has the four usual elements. The pharyngobranchials of the second, third, and fourth arches are broad and articulated into one rough mass above the pharynx. The third hypobranchial has a small ventral hook partially enclosing, with its fellow, the ventral aorta, while the fourth arch has no hypobranchial.

The fifth arch consists on each side of a single lower pharyngeal bone with fine villiform projections. The copulæ are: First, a long cartilage-tipped ossification, lying mainly between the first hypobranchials. The second separates the second and third hypobranchials; its anterior third is cartilaginous. Sometimes there is a small nodule—copula 3—separating No. 2 from No. 4, a diamond-shaped cartilage touching the third hypobranchials by its anterior borders, and the fourth ceratobranchials by its posterior edges. The parosteal gill-rakers, movably attached, are short and dagger-like, and occur as far back as the front border of the fourth arch.

6. Pectoral Girdle.—The pectoral girdle is very strongly developed; its ventral moiety is carried far forward to be vertically beneath the orbit, behind and below the urohyal, and its anterior edge is largely hidden by the operculum and branchiostegal membrane. The post-temporal, unforked and triangular, is firmly fixed by its sculptured surface to the auditory region of the skull: with the opisthotic it forms a good socket for receiving the head of the supra-clavicle. The latter, strong and rectangular, covers a long vertical process of the clavicle, and below enters a groove on that bone. The clavicle, the largest bone in the body, forms a curve with its convexity downwards and backwards. The anterior process of its forked dorsal end abuts against the opisthotic process. The outer surface presents a long ridge, expanded into a granular disc in its upper half. The inner surface also has a long ridge, which forms a strong connection with the upper anterior end of the pelvic girdle, and which in front forms a low rectangular area immovably articulated with its fellow of the opposite side. The clavicle bears two postclavicles, the upper a small plate carrying the styliform lower bone. The scapula, perforated by a foramen, is a small rhomboid partially interposed between the posterior end of the coracoid and the clavicle. The hatchet-shaped coracoid covers immovably, by the anterior end of its flattened handle, the front of the clavicle, and its posterior border is not indented. The four brachials, carrying each two fin rays, are borne equally, by the scapula and the coracoid.

7. The Pelvic Girdle.—The pelvic girdle (or basipterygium?) consists of a pair of very strong ossifications uniting by two symphyses, and interposed wedgelike, by a mobile connection, between the two clavicles. Each bone consists of two

triangles uniting in a thick bar, which meets its fellow in a strong symphysis. The posterior part of the bar bears a long process, extending both in front and behind, and meeting its fellow in a long second symphysis.

8. Vertebral Column.—The vertebral column consists of thirty-six undoubted vertebræ and a hypural, supporting twenty-nine or thirty dorsal interspinous bones, 8–10 ventral interspinous bones, and twenty-eight caudal rays. The short amphicœlous centrum is a well - ossified cylinder, with lateral strengthening ridges. The perforated neural processes bear small anterior zygapophyses. Behind each main hæmal process there is a small free subsidiary process. Above the level of the nerve foramen the atlas bears a riblike bone, the position of whose head seems to correspond to that of the epineural of Owen. Similar bones for the following vertebræ are attached to processes successively more distinct, and springing from lower levels, until on No. 5 they spring from the centrum. In No. 6 there appears a small bone attached by fibrous tissue to the middle of the undersurface of the riblike bone, usurping the position of the end of the latter over the cœlome. The ventral element is longer in No. 7, and nearer the centrum, which it reaches in No. 8, where it has the position of an ordinary true rib. In 9–12 the dorsal riblike bone is smaller, and is now clearly “intermuscular.” Thus it would appear that the first five vertebræ have no true ribs, but only intermuscular bones. Now, compare the last dorsal and first caudal vertebræ (Nos. 15 and 16). The former has its transverse processes very low down, and connected below (as also occurs in 13 and 14) by a bony bridge separating the caudal artery from the vein. No. 16 has a complete hæmal arch, partially marked into two divisions for the artery and the vein. No. 15 has a pair of ribs, lying close together, parallel to the large hæmal spine of No. 16. This spine is grooved in front, and lateral markings seem to point to a homology to the ribs of 15. The hypural consists of a demicentrum with neural and hæmal canals, and two fanlike plates, of which the upper bears two partially ankylosed pieces like neural spines. The pterygiophores or interspinous bones of the dorsal have each a triangular body with two lateral supports, and a head consisting of a horizontal plate. This plate bears an articular surface, behind which arises a curved process entering the perfect ring of the head of the dorsal spine, and almost meeting a long process from the head of the preceding plate. This amounts to the interlocking of two rings. The four anterior pterygiophores form a sutured structure lying above the skull, but, boiling, the parts are separable from each other and from the spines. The first, however, having