UPPER, OR FLINTY CHALK. 235 



Abdominales. 



The abdominal fishes are more frequent in the mineral kingdom, than 

 those of any other order ; they are distinguished by the ventral fins being 

 placed behind the pectoral, or upon the abdomen. The remains of three 

 species, belonging to as many genera, have been discovered in the Sussex 

 chalk, all of which appear to differ from any previously noticed, either in a 

 recent, or fossil state. 



The first that claims our attention, is nearly related to the genera Salmo 

 and Clupea, but does not entirely conform to the characters of either ; it 

 may however be convenient to affix some name as a temporary distinction, 

 and for reasons hereafter mentioned, the following has been selected. 



114, Salmo Lewesiensis. Tab. xxxiii. fig. 12. Tab, xl. fig. 1. 



The body of this ichthyoHte is of an elongated oval form, and covered 

 with smooth, delicate, semicircular scales. The trunk is subcyUndrical, 

 the back shghtly ridged, and the abdomen rounded. The head, so far as 

 can be ascertained from the specimens in my collection, appears to have 

 been of an obtuse form. The eyes are placed high on the head; the mouth 

 and jaws resemble those of the Salmo odoe, but no vestiges of teeth are 

 perceptible; the hps are rounded as in the Perch (Percajluviatilis.) The 

 opercula branchialia consist of three or four plates, and in one example ten 

 or eleven of the branchiostegous rays remain. The pectoral fins lie close 

 to the gill-covers, and are composed of seven or more rays. The ventral 

 fins are attached to the abdomen, and each has six or seven rays. The 

 dorsal and caudal fins are unknown ; but the small adipose fin or process, 

 so constantly observable between the dorsal fin and tail, in the recent 

 fishes of the salmon tribe, is distinctly shewn in one specimen. 



The ventral fins being situated behind the pectoral, places this fossil 

 fish in the order abdominales ; while the relative situation of these parts, 

 the adipose dorsal appendage, the structure of the opercula, and the 

 rounded form of the abdomen, prove its affinity to the salmo. The ab- 

 sence of teeth, and the obtuse form of the head, appear to distinguish it 

 from the recent species. 



Tab, xl. fig, ] . The body of S, Lewesiensis attached to a block of chalk ; 



H H 2 



