568 On the true Corals dredged by H.M.S. ' Challenger.' 



From the foregoing list it will be seen that 17 genera out of 42 

 obtained hitherto in depths of 50 fathoms and upwards belong to the 

 TurbinolidaD ; and if, following Pourtales, we placed with the Turbinolidae 

 the genera Parasmilia, Coelosmilia, and Solenosmilia, there would be 

 twenty genera of Turbinolidae. The family next most abundant in 

 genera is that of the Stylasteridae, which has six genera in the list. 

 Further, twenty-six of the genera in the list are those of simple corals, 

 and only sixteen genera of compound forms. The excess of the genera 

 of the Turbinolidae is what might be expected, since this is the family 

 which contains most extratropical shallower-water forms, and which 

 may thus be supposed to be bes't suited to low temperatures at consider- 

 able depths. With regard to the genera and species procured by the 

 1 Challenger/ it will be remarked that the genera Coenocyathus, Acantho- 

 cyathus, Platytrochus, and Ceratotrochus amongst the Turbinolidae are 

 new additions to the deep-sea coral-fauna. The four species described 

 under the genus Ceratotrochus may give rise to one or two new allied 

 genera. Amongst the Oculinidae, Cyathohelia is new to the deep sea. 

 Amongst the Astraeidae the occurrence of a genus of Astraeaceae at 126 

 fathoms is remarkable and quite exceptional. The coral is a very small 

 and dwarfed form, of which I have not determined the genus ; it occurs 

 also in the Arafura Sea in 49 fathoms in company with Flabellum varia- 

 bile and Phodopsammia parallela and socialis. Amongst the Eupsam- 

 midae the genus of Btephanophyllia is a new phenomenon, and the two 

 species obtained appear to be of great interest, and likely to throw much 

 light on fossil forms. 



On the occurrence of Fossil forms in the Deep-Sea Fauna. 

 Of the forty-two genera on the list just given twenty occur in the 

 fossil state. Eight of these occur in Secondary formations, viz. Caryo- 

 phyllia, BatJiycyathus, Trochocyathus, Thecocyaihus, Amphihelia, Para- 

 smilia, Coelosmilia, and Stephanophyllia. Of these, two extend into the 

 Jura formations, viz. Trochocyathus and Coelosmilia ; the remainder are not 

 known from earlier deposits than the chalk. The remaining genera of the 

 list are known only from Tertiary formations. Of these twenty genera, 

 however, thirteen were known before deep-sea dredging commenced, to 

 occur both in the recent and fossil condition, and hence they must occur 

 in not very deep water, whilst some of them, as Caryophyllia and Fla- 

 bellum, occur in very moderate depths. Seven of the fossil genera, viz. 

 Trochocyathus *, Thecocyaihus, Deltocyaihus, Platytrochus, Ceratotrochus, 

 Parasmilia, and Stephanophyllia, have been added to the list of fossil 

 genera, which have survived to the present epoch, by deep-sea dredging. 

 Of the twenty fossil genera above referred to, thirteen only occur at so 

 great a depth as 250 fathoms, eight are found at 500 fathoms, seven at 



* Trochocyathus philippensis (Semper), however, occurs at the Philippines in from 

 15-30 fathoms. 



