ON DORYPTERUS HOFFMANNI. 2-A7 



individuals of this species which I saw at Mr. Althaus's are of 

 equal size, but both without scales, so that only the skeleton of 

 the fish is seen, an appearance very common in the lithographic 

 slates of Bavaria, but very rare in the Kupferschiefer. One 

 recognizes pretty clearly the very strange composition of the 

 skeleton of this fish, which Agassiz has fully described in ' Ee- 

 cherches sur les Poissons Fossiles.' Only faint impressions exist 

 of each individual. 



" The individual figured (tab. v., f. 2), which Mr. Althaus was 

 so kind as to let me have, has at the first superficial glance some 

 resemblance in its external form to Platysomus gibbosus, Agassiz, 

 so that at first I thought this might be only the skeleton of a 

 young individual of that species ; but a stricter investigation and 

 comparison soon convinced me that it is an entirely new species. 



" The body has a rounded rhomboidal, nearly ovate form. The 

 head is disproportionately large, and occupies nearly one half of 

 the body ; its profile from the dorsal fin to the snout is some- 

 what straight ; the snout much bent. The large orbit is placed 

 high and far backwards. The faint impressions of the head-bones 

 are smooth, without striae or granulations ; but their appearance 

 is not very distinct. The hind border of the operculum or gill- 

 plate is narrow ; near to it is placed the left pectoral fin, which 

 has probably been pushed so high up by pressure from without. 

 One recognizes only the impressions of a few rays : below, on 

 the margin near the anal, the rays of a small fin are shown, which 

 appear to have belonged to the ventral ; for although, until now, 

 on the specimens of the genus Platysomus, which have been exa- 

 mined by Agassiz, Grermar, and others, ventral fins have not been 

 seen, yet I have found them on two examples of P. Fitldai 

 (=Platysomus macrurus, Ag.). 



" The dorsal fin is somewhat large ; the commencement of it 

 is near the head, in the central part of the back. The anal stands 

 opposite to it, and is nearly of the same form and size, but is 

 situated nearer to the mouth than to the tail, for it reaches nearly 

 to the head. The rays of both fins run to the tail, and are very 

 fine. On the example before us, fragments only of the rays of 

 the continuation of the dorsal could be seen. 



