BRITISH FOSSILS. 



Decade IX. Plate YI. 



NOTHOSOMUS. Gen. Nov. 



[Genus NOTHOSOMUS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. 

 Order Goniolepidoti. Eamily Lepidostei. Sub-family Lepidostei homocerci. 2nd 

 Group, body elongated, more or less fusiform.) Eins small, with fulcra on the first 

 rays. Caudal fin forked. Scales smooth ; four rows of broad scales on the flanks.] 



Noihosomus octostychiiis. Agassiz. Poiss. Foss. vol. 2, page 292, 



The genus Nothosomus is notified in the " Recherches sur les 

 Poissons Fossiles " of Agassiz in the following terms : — " After the 

 genus Ophiopsis must be placed a new generic type, which I have 

 distinguished by the name Koiliosomiis, and which is characterized 

 by a long dorsal fin and scales higher than broad.'' The specimen 

 from which the genus was established was found in the Lias at 

 Street, and presented to me by Mr. Hawkins. It only shows the 

 posterior half of the fish, but as it is the type of the genus, and so 

 far as I am aware the only example of it which has yet been found, 

 it is worthy of being described, the more so that in consequence of 

 the brief notice of Professor Agassiz, it has been quoted by other 

 authors, and is included in all the catalogues of liassic fossils. 



Description, — The specimen is broken off* immediately in front 

 of the dorsal fin, and the anterior portion is Vv^anting. What 

 remains is, however, in a good state of preservation, and exhibits 

 the dorsal, ventral, anal, and caudal fins, together with the scales of 

 the right flank seen from within. A few impressions of the outer 

 surface of the scales are seen in the anterior part of the specimen. 

 The dorsal fin is situated a little in advance of a perpendicular line 

 extended from the attachment of the ventral fins ; the anal fin is 

 inserted about midway between the ventrals and the base of the 

 tail. The interspace between the first ray of the dorsal fin and 

 the upper lobe of the caudal fin measures two inches and a half, 

 and from the ventral fin to the lower lobe of the tail two inches 

 and one tenth. The depth of the trunk from the dorsal fin to the 

 ventral fins is one inch and three quarters ; fi'om this point to 

 the spring of the caudal fin, where the diameter is half an inch, 

 the contraction is very regular. In these details Nothosomus bears 

 [IX, vi.] 9 G 



