BRITISH FOSSILS. 



Decade IX. Plate IV. 



ENDACTIS. Gen. Nov. 



[Genus ENDACTIS. Agassiz. (Sub-kingdom Vertebrata. Class Pisces. Order 

 Goniolepidoti. Eamily Sauroidei. Sub- family Sauroidei homocerci. 1st Group, tail 

 forked.) Head small and pointed ; dorsal fin opposite the ventral fins ; anal fin approxi- 

 mated to the ventral fins ; base of the tail deep ; scales minute, curvilinear, ornamented 

 with raised surface markings.] 



Species Unica. Endactis Agassizi. 



The subject of the following description is the last fossil fish 

 named by Professor Agassiz before his departure for the United 

 States. I had incorporated it in my cabinet as a new species of 

 Packycormus, but his discriminating eye detected evidences of 

 generic discrepancy which induced him to make it the type of a 

 new genus, Avhich he called Endactis from the peculiar character of 

 the scales. It certainly is very nearly allied to the Pachycormi in 

 general figure, and in the arrangement of the fins ; the most 

 evident distinctions being the larger size of the dorsal fin, the 

 greater thickness of the caudal pedicle and the surface ornament of 

 the scales. It is, perhaps, hazardous to trust to characters so 

 slight, and to the evidence of a single specimen, and that an imper- 

 fect one for generic isolation; the more so when we find some 

 of these characters variable and considered as of only specific 

 value in the several species of Pachycormus with which we are 

 acquainted. A very important element for deciding the ques- 

 tion is unfortunately deficient, namely, the caudal fin. One of 

 the most striking and constant peculiarities of the genus Pachy- 

 cormus is a very large and deeply cleft caudal fin springing from 

 a narrow pedicle, caused by the rapid contraction of the dimensions 

 of the after part of the trunk. This contraction is much less 

 rapid in Endactis, as far as the specimen shows, and I am inclined 

 for this reason to believe that future discoveries will reveal a form 

 of caudal fin which will substantiate this as a generic type. Should 

 it prove otherwise, the genus must lapse, but there is no doubt 

 [ix. iv.] 9 E 



