ON DORYPTERUS HOFFMANNI. 249 



Dorypterus is pretty regularly oval in contour, inclining to 

 ovate, the posterior slopes being more rapid than the anterior, 

 and the head rather obtuse. It was probably much compressed, 

 and is very deep in proportion to its length ; the length of the 

 body, including the central rays of the tail, is about twice its 

 depth at the deepest part. Our largest specimen is five inches 

 long, including the tail, and two inches and a quarter deep ; and 

 the head, from the anterior extremity of the mandible to the 

 posterior angle of the gill-plate, is about one-third the length of 

 the entire animal, including the centre rays of the tail. The 

 muzzle is obtuse, the mouth shutting upwards ; the mandibles 

 are long, flat, and rather wide ; the praemaxillse are about half 

 the length of the mandibles, and, like them, are flattened and 

 wide ; the maxillae are about as long as the praemaxilke, and 

 bend downwards, and overlap the posterior portions of the 

 mandibles. The gape was large ; and the jaws probably shot 

 out a little when in action ; no teeth have been observed. 



The orbits (PL IX., fig. 1', u) are large, and are situated im- 

 mediately behind the praemaxillas and a little below the brow or 

 dorsal ridge : the gill-plate or operculum (s). seems to be com- 

 posed of two pieces, and is of a narrow crescent-form, the pos- 

 terior margin being a little angulated, the angle projecting above 

 the middle longitudinal line of the body. The prseoperculum (t) 

 partakes of the same form, but is considerably less than the 

 operculum, and is placed midway between the eye and the pos- 

 terior margin of the gill-plate. 



The clavicle (r), which is well preserved in one of the speci- 

 mens, is a long, stout, fusiform bone, extending from above the 

 longitudinal middle fine of the body to the insertion of the vent- 

 ral fin, and is well inclined thence upwards and backwards. 



The pectoral fins (c), which are eight-tenths of an inch long, 

 are wide and somewhat rounded, the extremity being obtuse ; 

 they are rather large in proportion to the size of the body, and 

 are situated just behind and below the angle of the operculum, 

 consequently on the central longitudinal line. They are con- 

 nected with the upper portion of the clavicle. The remains of 

 apparently the scapula and coracoid were observed in one of the 



