THREE CRUISES OF THE 'BLAKE. 



animal kingdom is under discussion, though they have until lately 

 been generally classed with the mollusks. As the brachiopods 

 date back to the Cambrian, it is natural that we should find it 

 difficult strictly to define their affinities with recent types, since 

 with very slight modifications they have persisted from remote 

 antiquity to the present day, during all the intervening con- 

 ditions of existence. 



Like the lamellibranchs, they are provided with two valves. 

 These, however, as well as the soft parts, are bilaterally sym- 

 metrical in relation to the longitudinal axis of the shell. 



The most common species we collected, Terebratula cubensis 

 (Figs. 313, 314), was discovered by Pourtales, in from 100 to 



Fig. 314 

 Terebratula cubensis. (Davidson.) 



270 fathoms, in rocky ground oft' Havana and from the east end 

 of the Florida Reef. It attaches itself by a short and stout pe- 

 duncle ; the shell is globular, nearly white, translucent. An- 

 other most abundant species associated with the former is Wald- 

 heimia floridana (Figs. 315, 316), which is common on rocky 



Fig-. 315. 



Waldbeimia floridana. 



Fig. 316. 



bottoms between 100 and 200 fathoms. It is of a grayish or 

 brownish white horn-color, and belongs to a group containing 

 many living and fossil species. Much less common, but with a 

 more solid test, is Terebratulina Cailleti. (Fig. 317.) This 



