296 MR. J. W. DATIS ON HETEROLEPIDOTUS GEANDIS, 



fulcral spines. The anal fin is not well preserved, but sufficient 

 remains to indicate that it was a strongly built and powerful 

 fin. 



The ventral fin is situated opposite to the dorsal. It was sup- 

 ported by a large pubic bone, a part of which, is preserved attached 

 to the base of the fin. The exact number of rays is not clearly 

 defined. They are strongest on the outer or anterior portion 

 of tbe fin, and gradually assume smaller proportions backwards. 

 The anterior ray was probably 4*5 inches in length ; nearly half 

 the length is unjointed ; beyond, it is divided by numerous arti- 

 culations and becomes rapidly divided into numerous filamentous 

 branches. The anterior margin of tie fin is strengthened by 

 numerous imbricating fulcral rays, averaging '5 inch in length, 

 and extending 3 inches from the base ; they are round in section, 

 and being considerably less in diameter than the fin-ray they 

 cluster round it, grouped in a more or less semicircular manner. 



The pectoral fin is composed of 24 rays. The anterior ones 

 are 8 inches in length, remarkably strong, and attached by a 

 peculiar articulation to tbe shoulder-girdle. The anterior rays 

 of this fin are represented, natural size, by the drawing on 

 Plate VII. fig. 3; and a reference to the figure will explain, 

 better than words, tbe form of tlie joint. The three anterior rays 

 are attached by a kind of ball-and-socket joint to a projection of 

 the scapular portion of the shoulder-girdle, a second portion of 

 whicb, or bones in connexion with it, whicb may be the equivalents 

 of the carpal bones of the bony fishes, descends towards the 

 posterior portion of the fin and supports the remaining fin-rays. 

 The fin-rays are simple and undivided to one third their length 

 from the base, beyond which they are articulated and dichotomize 

 repeatedly. A number of small imbricated rays are attached to 

 the anterior fin-rays ; compared, however, with those of the other 

 fins they are small and inconspicuous. 



The genus Seterolepidotus was instituted by Sir Philip 

 Egerton for the reception of fishes in many respects closely 

 related to Lepidotus, Ag., but diflFering from that genus in their 

 dentition, and more especially in the form and arrangement of 

 the scales of the body. In LepidoUos the scales are uniform in 

 size over the whole surface of the body ; but in Seterolepidotus 

 the scales on the ventral and abdominal surfaces of the body are 

 greatly elongated and much resemble the long and narrow scales 



