276 PEQCEEDINGS OF THE GE0106ICAL SOCIETY. [A^pr- 5, 



size compared with the surviving types of the family. The recent 

 discovery of a specimen in the Lias of Lyme Eegis, in which a 

 considerable portion of the anterior structures of a Chimseroid is 

 preserved, enables me to advance a step in clearing up the mystery 

 which has hitherto shrouded this subject. It was described to 

 mo as a new species of shark, showing the dorsal spine in situ, 

 and the upper and lower jaws. Prom a rough sketch of the spe- 

 cimen forwarded with the letter, I was inclined to think, from 

 the peculiar mode of insertion of the spine, that it might possibly 

 belong to a Balistes or a Siluroid fish, certainly that it could not be 

 a shark ; but on examining the specimen itself I found the unmis- 

 takable dental apparatus characteristic of the Chimseroid s, sur- 

 rounded with shagreen ; and then perceived that what was described 

 as the upper jaw of a shark could only be a monstrous form of the 

 singular rostral appendage peculiar to the male sex of the Chi- 

 maeroids of the present time. The dermal integument has fortu- 

 nately retained its proper position and outline on the frontal and 

 oral regions, representing a tolerably correct profile of the head. 

 The forehead is characterized by a remarkable prolongation of the 

 skin (PI. XIII. fig. la), extending six inches beyond the frontal carti- 

 lages, and terminating in a hook directed abruptly downwards for 

 more than one inch. This structure is very similar to the prelabial 

 appendage found in the C'allorJiynchus antarcticus of the present period. 

 Immediately above this projection, and following the outline of its 

 upper margin, is seen what I imagine to be the homologue of the 

 frontal ossicle of the recent male Chimasroids (1 b). In the latter it 

 exists as a small incurved bone, terminating in a kind of pad covered 

 with minute spines ; but in the fossil it is developed into a formidable 

 rostrum slightly curved at the base, forming a frontal declivity, and 

 then projecting forwards as far as the extremity of the prelabial 

 appendage above described. Its entire length is five inches and a 

 half, of which the anterior two-thirds are straight. The proximal 

 extremity is attached to the head by means of a rounded condyle, 

 which is received in a hollow of the frontal cartilage — an arrange- 

 ment which allows of a limited amount of motion in the vertical 

 plane. The underside of the rostrum is thickly beset with tubercles 

 carrying recurved central spines, not unlike the dermal tubercles ol 

 some of the recent Haiidce. Similar spine-bearing tubercles, seated 

 on the upper surface of the nasal prolongation, are opposed to the 

 former, so that a fragmentary specimen of this portion of the fish 

 might easily be mistaken for parts of an upper and lower jaw. The 

 tubercles extend in diminished size and numbers along the entire 

 under surface of the organ. The upper surface was covered by 

 coarse-grained shagreen, which probably invested also the sides ; 

 but it has perished in these parts, and the coarse fibrous structure 

 of the bone is displayed. About one inch behind the insertion of 

 the frontal spine the orbit is seen. This is of large size, measuring 

 one inch in diameter. Two inches behind the orbit, and in close 

 proximity to the occipital region, the dorsal spine (Ic) is situated. 

 Before, however, entering upon the description of this organ, it will 



