ON PLATYSOMUS ROTUNDUS. 411 



From the above description it will be perceived that Pleurodus 

 is a not very distant ally, as we have already stated, of Wodnika, 

 of the Kupferschiefer of Germany, the relationship being seen 

 in the characters of the spine and shagreen, and particularly in 

 the form of the teeth : in both genera they have the same boss- 

 like, carinated crown, with expanded lateral margins, more or 

 less ridged or crenate ; in both, too, they are coarsely punctate, 

 and covered with a stout, highly polished enamel. 



We are thus assured that Plexirodus is a Cestraciont ; and such 

 being the case, its small size is very remarkable. But it must 

 be mentioned that if the large teeth are mere varieties of the 

 small and usual form, then our specimen may not by any means 

 be fully grown ; however, after making every allowance for in- 

 crease in size on this account, still the species would be a very 

 small Cestraciont, most of which are of considerable dimensions. 

 Wodnika, which is a small species, judging from Minister's figure,* 

 cannot have been less than a foot long. It is nevertheless quite 

 possible that our specimen is, notwithstanding, a fully developed 

 individual. This is rendered probable by the fact that the teeth 

 in connexion with it are of the usual size of those found detached 

 at Newsham; and of such we possess thirty or forty: some 

 of these are smaller than those connected with the specimen ; 

 scarcely any are larger ; or, if so, there is a mere shade of dif- 

 ference in this respect. In the separate head before alluded to, 

 the teeth are likewise of the usual size ; and the second or de- 

 tached spine already mentioned is not quite so large as that in 

 connexion with the fish. 



Platysomus eotundus, n. sp. 



A very distinct and beautiful species of Platysomus has oc- 

 curred at Newsham ; three almost perfect specimens of it have 

 been met with, and four or five considerable portions, all of 

 which exactly agree in character, though they vary a little in 

 size. The largest and most perfect specimen is three inches 

 long, measured from the clavicle to the end of the tail-fin, and 

 is two inches and three-quarters deep at the widest part. It is 



* Beitrage, Heft vi., p. 4S, Taf. 1, fig. 1 a to d. 



