70 THE VOYAGE OF H.M.S. CHALLENGER. 



regarded as a permanent larval form. The absence of the pinnules from the lower parts 

 of the arms points to the same conclusion, as has been explained elsewhere. 1 



I have only been able to examine the disk in the two Challenger specimens, and in 

 one of these it is not very well preserved. But they both agree in the slightly excentric 

 position of the mouth, and in the large size of the peristome, so that the anal tube is 

 pushed backwards behind the centre about as much as the mouth is in front of it 

 (PL VI. figs. 4, 6). 



Unlike the two Endocyclic Comatulse with five rays and a rosette (Antedbn and 

 Eudiocrinus), Atelecrinus is not a littoral type at all, nor does it extend upwards above 

 200 fathoms. On the other hand it is not known to occur below 610 fathoms ; so that 

 bathymetrically it falls very far short of the archaic Thaumatocrinus (1800 fathoms). 

 Apart from this last type, however, the geographical range of Atelecrinus, although 

 fairly extensive, is the least so of the five-rayed Coniatulse. In the Caribbean Sea and 

 the East Atlantic it ranges from 24° N. to 9° S.; while it also occurs in the Pacific near 

 Fiji in 19° S. If the fossil calyx mentioned by Schliiter 2 as having persistent basals also 

 belong to this genus, it will date back to the Cretaceous period. 



The three existing species of A telecrinus may be distinguished from one another as 

 follows : — 



I. Second radials transversely oblong and but little incised. Basals not specially 



prominent at the angles of the calyx, . . . . .1. balanuides, n. sp. 



II. Second radials markedly incised and about as long as wide. 



A. Basals separated from the centro-dorsal at its interradial angles, . 2. wyvillii, n. sp. 



B. Basals produced outwards at the interradial angles, . . .3. eubensis, Pourtales, sp. 



1. Atelecrinus balanoides, n. sp. (PL VI. figs. 6, 7). 



1879. Antedon eubensis, Pourtales (pars), Bull. Mus. Comp. Zobl., 1879, vol. v. No. 9, p. 214. 



1881. Atelecrinus balanoides, P. H. Carpenter, Bull. Mus. Comp. Zool., 1881, vol. ix. No. 4, 



p. 16, pi. i. figs. 1-6. 



1882. Atelecrinus balanoides, P. H. Carpenter, Journ. Linn. Soc. Lond. (Zool.), 1882, vol. xvi. 



p. 489. 



Centro-dorsal acorn-shaped, reaching 5 mm. high by nearly 35 mm. in diameter. 

 It bears five vertical double rows of cirrus sockets, the upper ends of which are separated 

 by more or less distinct interradial ridges. Four to six sockets in each row, the dorsal 

 pole, though rough, being free from functional sockets. The ends of their horseshoe- 

 shaped rims slant downwards and outwards, but are much more prominent in some 

 individuals than in others. 



The cirri have three or four quite short, almost triangular basal joints. The next is 

 two or three times as long as wide, and its successors are much elongated, reaching 

 2"5 mm., with a slight tendency to overlap one another on the ventral side of the cirrus. 



1 Bull. Mus. Comp. Zobl., 1882, vol. ix. No. 4, pp. 14, 15. 2 Zeitschr. d. deutsch. gcol. Gesellsch, 1878, p. 60. 



