86 MESSRS. HANCOCK AND ATTHEY ON 



Huxley founds the genus Rhizodoiysis'^ have occurred at Newsham. 

 They are all in a very incomplete state, though, y^iih. the aid of 

 the whole series, many of the characters can be determined. 

 The most perfect specimens are between five and six inches in 

 length ; the largest is eight inches long, exclusive of the tail, 

 which is wanting ; and the smallest is not more than two or 

 three inches in extent. There is proof, however, that this spe- 

 cies sometimes attains a considerable size. A crushed head has 

 been found that measures nearly 3^ inches in length ; and ossi- 

 fied vertebral rings have occurred that are i%ths of an inch in 

 diameter. 



In all respects our specimens agree well with Dr, Young's de- 

 scription of this species in the "Journal" Geological Society. 

 (loc. cit.) The scales are usually well preserved ; all the fins, as 

 well as the tail, can be determined ; and the gill opercles, man- 

 dibles, and upper jaws, in a more or less entire state, with the 

 teeth attached, are all displayed. 



The scales vary, of course, greatly in size. On the smallest 

 fish they cannot be more than ^ih. of an inch long, while large 

 detached scales measure an inch in length. They are all, how- 

 ever, so perfectly similar that it is impossible to deny their spe- 

 cific identity. The coarseness of the surface sculpture and the 

 thickness of the scale vary, as might be expected, with its size ; 

 but no other difi'erence can be detected. It is therefore only 

 left us to follow the prudent caution of Dr. Young, and to wait 

 for further information before doing anything so rash as to divide 

 specifically the thin and delicate from the thick and compara- 

 tively coarse scales. There is one character, however, which 

 seems to have escaped the notice of this palasontologist, and 

 which is pretty distinct in one or two of our examples. The 

 dorsal and ventral fins are protected in front by a series of thick 

 enamelled scales, which are brilliantly glossy and minutely punc- 

 tured, not at all like the body scales, but similar to those in front 

 of the fins in Megalichthys. The first or proximal scale is very 

 stout, if not a solid cylinder, and is f ths of an inch long, it looks 

 almost like the base of a spine, but is probably composed of two 



* " Quarterly Jonrnal" Geological Society, Vol. XXII.. p. 59G, 1S66. 



