CHARACTERISTIC DEEP-SEA TYPES. CORALS. 



149 



cv>^ 



Two species of the genus Tliecocyathus have been dredged, 

 and are not uncommon in from 100 to 315 

 fathoms. One of these, T. cyllndraceus, is 

 here figured. (Fig. 4G1:.) The genus is inter- 

 esting as dating back to the lias ; it is not 

 known from any of the formations inter- 

 mediate between the Has and our epoch. 

 The recent forms present, therefore, a com- 

 paratively rare instance of the reappearance 

 of a genus apparently extinct through a con- 

 siderable succession of ao-es. 



Deltocyathus italicus (Figs. 4S5, 465 a-d) is an exceedingly 



Fig. 4()4. — iiiecoeya- 

 tliiis cylindraceiis. 

 (Pouitales. ) 



3 



1" 





■f®?^ 





Fig. 4fi5 a. 





-^•'^S5» 



'nn 



Fig. 465 c. 



MufW^ 



Fia-. 46.5 d. 



Deltocyatlms italicus. |. (Pourtales.) 



*ii. 



mMW^ 



Fijr. 465 6. 



variable living form of a tertiary fossil common in Sicily. The 

 polyp of a large living specimen, dredged in 115 fathoms off 

 the Tortugas, was whitish, with short club - shaped tentacles. 

 A most variable species is Paracycdhus confertus. (Fig. 466.) 

 Stephanotrochus diadema (Fig. 467) seems to be a character- 

 istic deep-sea type. It has been dredged in 734 fathoms off 



