132 THE VOYAGE OF H.M.S. CHALLENGER. 
and the genus Leptopenus, which has as yet been dredged only south of the equator, 
but both in the South Atlantic, South Indian, and South Pacific Oceans in very great 
depths. 
No examples of any of the species of the genus Stephanotrochus were obtained in 
the Pacific Ocean. They have hitherto occurred only in the Atlantic and South Indian 
Oceans. I have taken care to give in the description of the figures at the end of this 
memoir the exact locality at which each specimen figured was dredged, because local 
varieties may at some future time be determined, and, moreover, forms placed and named 
together may hereafter be separated. 
The wide range in depth of some species is very remarkable, and the instance of Bathy- 
actis symmetrica has often been referred to since the Challenger Expedition returned ; it 
ranges from a depth of 70 fathoms in the tropics to one of 2900 fathoms. The following 
table gives the depths at which all genera of corals which have as yet been found at a 
depth of 50 fathoms and upwards occur. The occurrence of the genera as fossils in 
Secondary and Tertiary deposits is also indicated. Some shallow water forms extend to 
very considerable depths. The deep-sea forms are not as a whole of greater geological 
antiquity than shallow water forms. 
TABLE showing the Depths at which all Genera of Corals, which have as yet been 
obtained in Depths of 50 Fathoms and upwards, are known to occur. 
The depths are given in round numbers, and the x’s indicating the ranges of the coral in depth are placed 
in those columns the numbers relating to which approach most nearly to the depths at which the corals 
have been actually dredged. Thus, ifa coral has been dredged at 76 fathoms, it is marked in the 100 
fathoms’ column ; if at 74, in the 50 fathoms’ column; if at 1126, in the 1250 column; if at 1124, in 
that of 1000 fathoms. 
| 
| | 
| Depths in Fathoms at which the several Genera occur. AGE. 
i] 
GENERA. ae y | | | | | | (ane : 
| = 3 fd a Tal a a a ie |o ‘ lo | =i Le 
| tac asic Weta lest tassel reese || cass |Nras a pss lies Silas B Sis o|s S|SP| as 
| ase = Lal Nn il oD a) wD ~ | oO i>) ws ~ o a ro} I~ oOo On aes 
Pale i ee rs | | CU MCN RoR oa = 
| | | ai | 
i] eae sl eclie mecca eles "le Vocal) eal scale tric ecg mae ean 
eee CEL toe oN liee co Il coeds |piovat cate Seo tea Hb aan pe | x |) SCG xXeiiexx 1 ex iat 
| | | 
Acanthocyathus | q x |x |x iat] 
| | | 
Stenocyathus  . Sex <a x<eias | 
| 
_Paracyathus . cata ead Be eccel lees esal tala oie | We || | e | 
| | 
| | 
| Leptocyathus . KK | SOx SR xe Tie | 
| . | : | 
| Schizocyuthus . eaulless th Soules | | 
[Deltocyathus | x}x]|x ix] x} xix] x] «txt x |x | x | | x 
| 
Trochocyathus . | x|x| x] x] x] x |x |x | | Pel 
| | | | 
ea ee Ge | All| alee seer Re eT wes 
| = tall =) S | oS > S =y |=: S | i=) > =) = oS S > =) 
| a8 Fay] et [Pew al eae liom cerquenco genes ese lees ace | reall ema ea Ce eal 
| De | | | | | Tt rc rm a alata oD 
