CORALS. 149 
CHARACTERISTIC DEEP-SEA TYPES. 
Two species of the genus Thecocyathus have been dredged, 
and are not uncommon in from 100 to 315 
fathoms. One of these, 7. cylindraceus, 1s 
here figured. (Fig. 464.) The genus is inter- 
esting as dating back to the las; it 1s not 
known from any of the formations inter- 
mediate between the lias and our epoch. 
The recent forms present, therefore, a com- 
paratively rare instance of the reappearance 
i Fig. 464. — Thecocya- 
of a genus apparently extinct through a con- thus eylindraceus. 
siderable succession of ages. î. (Pourtalès.) 
Deltocyathus italicus (Figs. 465, 465 a-d) is an exceedingly 
Fig. 405 d. 
Fig. 465. 
2 
Deltocyathus italicus. 2. (Pourtalès.) 
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 Paracyathus confertus. (Fig. 466.) 
Stephanotrochus diadema (Fig. 467) seems to be a character- 
istic deep-sea type. It has been dredged in 734 fathoms off 
