CHARACTERISTIC DEEP-SEA TYPES. BRACHIOPODS. 77 



small species extends to a depth of nearly 500 fathoms. A 

 most common Atlantic species, T. caput-serpentis (Fig. 318), is 

 found along the eastern coast of the United States as far south 



Fig-. 317. Terebratulina 

 Cailleti. f. (Davidson.) 



Fig. 318. Terebratula caput- 

 serpentis. l^fA (Davidson.) 



as Cape Cod. A species of Platydia, identical with the Medi- 

 terranean P. anomioides (Figs. 319, 320), has been dredged by 

 the " Blake " in 237 fathoms. It represents the group of brach- 

 iopods with shells having loops and conspicuous perforations. 



Fig. 319. 



Platydia anomioides. 



Fig. 320. 

 (Davidson.) 



A few specimens of Crania (Fig. 321), a genus not before 

 obtained on the American coast, were dredged by Pourtales off 

 the Samboes and Sand Key, at 

 depths ranging between 100 and 

 200 fathoms. Living specimens of 

 Dissina atlantica (Fig. 322) have 

 been taken by the " Blake " and by 

 the Fish Commission at the depth 

 of over 2,000 fathoms. They are 

 usually attached to concretions. 



Fig. 321. 

 Crania Pourta- 

 lesii. 25 -. (Dall.) 



Fig. 322. Discina 

 atlantica. \ . (Ver- 

 rill.) 



The simple and compound ASCIDIANS are eminently littoral 

 and shallow- water types, and but few of them extend to any 

 great depth. Neither the " Blake " nor the " Challenger " col- 

 lected any very remarkable abyssal types, and the species were 

 either closely allied to or identical with well-known genera. 



