110 MESSRS. HANCOCK AND ATTHEY ON 



expanded base. There can be little doubt that these are carpal 

 bones, similar to those in connexion with the pectoral fins in the 

 sharks and dogfishes. This bone is thickest at the apex, which 

 is rounded, and thins out towards the distal expanded margin or 

 base. The large longitudinal groove at the root of the spine pro- 

 bably corresponds to the lower or anterior margin of this bone ; 

 or it may be that it was fitted to a lower carpal which was co- 

 adjusted to this bone, but, being entirely cartilaginous, has dis- 

 appeared. However this may be, it can scarcely be doubted 

 that this triangular bone supported, directly or indirectly, the 

 great pectoral spines. 



There are found also frequently associated with the remains of 

 Gyracanthus large thin layers or patches of matter, almost en- 

 tirely composed of minute compressed bodies, of which there are 

 two kinds. One, much smaller than the other, and by far the 

 more numerous, is upwards of -2-0-th of an inch high, and not 

 quite so broad ; it has usually two, sometimes three, conical, re- 

 curved, diverging points rising from an expanded base. The 

 large kind is usually xb-th of an inch high, and is somewhat 

 wider at the base ; it is sometimes a little larger, but more fre- 

 quently much smaller. It is much compressed, and the base is 

 considerably widened ; the upper margin is divided into from 

 four to seven much recurved conical denticles, which are sharp 

 pointed, and have four or five stout longitudinal ridges on the 

 arched or dorsal surface. Several large patches of these bodies 

 have occurred, one of which measures twenty inches by fifteen 

 inches. It is therefore pretty clear that they cannot be teeth, 

 which are not usually found together in such vast multitudes ; 

 they are much more likely to be dermal tubercles, and these 

 patches to be the remains of the skin of Gyracanthus. It should 

 also be mentioned that Cladodus mirabilis has occurred three or 

 four times at Newsham, and always associated with these der- 

 mal patches. May it not, therefore, prove to be the tooth of 

 Gyracanthus ? 



Note. — Mitrodus quadricornis of Professor Owen (pi. 3) is un- 

 doubtedly nothing more than the larger kind of these dermal 



