| OCR Text |
Show 140 PROF. R. COLLETT ON A [Mar. 2, the last is, however, in the uninjured specimen scarcely perceptible beyond the common skin which covers the head. The length of the head from the end of the lower jaw to the base of the spine on the operculum is to the total length as 1 to 2*7, this measured to the end of the caudal fin, but only 1-9 in the length to the root of the caudal. Thus the head is about the same as the rest of the body without the caudal fin. The highest part of the skull is indicated by a protuberance at the back of the head, probably formed by the point in which the os mastoideum (occipit. posterius) adjoins to the shoulder-girdle. The mouth is enormously large, with the cleft oblique; the lower jaw is slightly longer than the intermaxillary, and has backwards a considerable width (or about \ of its length). The length of the jaws is to the total length (to the end of caudal fin) as 1 to 2,8-3,0. At the back of the lower jaw there is a spine slanting inwards and downwards, the length of which scarcely equals the orbital spines. The eyes are well developed, although small on the whole; the lens is particularly small (about 1 millim.). The diameter of the eye is about 2*5 millim.; it is placed somewhat far forward, or a little more than two orbital diameters from the margin of the upper jaw. The gill-covers are but incompletely ossified, but their construction cannot be properly examined in this single specimen. The operculum is present as a long styliforra bone, which towards its lowest end sends out a backward-directed spine the length of which is 3 millim. (which, however, is completely enveloped in the common skin of the head). The prceoperculum appears to be unossified. The gill-openings are extremely small, and are situated at a distance of about half an eye's diameter below the pectoral fins ; they form a crescent-formed slit, the height of which is only 2"2 millim. The gills are 2 | pairs, as the second and third branchial arches have a double series, the fourth a uniserial gill. Pseudobranchice are wanting. The branchial arches are smooth on their inner surface, without a trace of protuberance or teeth. The branchiostegals appear to be but five in number; and I cannot, in this little and frail specimen, discover a sixth, which may possibly exist. The teeth are placed in a single row in each half jaw, with a distinct space between each tooth, and consist of long and slender teeth, some of which are very long, while the rest are somewhat shorter. They are finely streaked throughout their length, pointed like awls, and movable inwards, so that the long front teeth lie backwards, the side teeth inwards. All of them are covered with a jet-black skin, the extension of which cannot with certainty be determined in this specimen ; a few of the shorter teeth are still completely covered with it; but the points of long teeth have probably always been bare. The number of teeth in each half of the jaw is 7-9, to which |
