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 mo7ith 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 up|)er jaw. 



The gill-covers arc but incompletely ossified, but their construction 

 cannot be properly examined in this single specimen. The operculum 

 is present as a long styliform 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. Fseudobranchice 

 are wanting. 



The branchial arches are smooth on their inner surface, without 

 a trace of protuberance or teeth. 



The brauchiostegals 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 



