VI.] 



SPECIES AND TIME. 



155 



brata there were fishes not belonging to the lowest but to 

 the very highest groups which are known to have ever been 

 developed, namely, the Elasmobranchs (the highly-organ- 

 ized sharks and rays), and the Ganoids, a group now poorly 

 represented, but for which the sturgeon may stand as a 

 type, and which in many important respects more nearly 

 resemble higher Yertebrata than do the ordinary or 



CUTTLE-FISH. 



A. Ventral aspect. B. Dorsal aspect 



osseous fishes. Fishes in which the ventral fins are placed 

 in front of the pectoral ones (i.e., jugular fishes) have been 

 generally considered to be comparatively modern forms. 

 But Prof. Huxley has kindly informed me that he has dis- 

 covered a jugular fish in the Permian deposits. 



Among the molluscous animals we have members of 

 the very highest known class, namely, the Cephalopods, or 

 cuttle-fish class ; and among articulated animals we find 

 Trilobites and Eurypterida, which do not belong to any 



