REPORT ON THE CRINOIDEA. 225 



Family Bourgueticrinid/E, de Loriol, 1882. 



Genus Bathycrinus, Wyville Thomson, 1872; emend. P. H. Carpenter, 1884. 

 Ilycrinus, Danielssen and Koren, Nyt Mag. f. Naturvidensk., 1877, Bd. xxiii. p. 4. 



Definition. — Stem consisting of dicebox-sliaped joints and attached by a branching root, 

 the joints above which bear no cirri. The upper part of the stem, immediately beneath the 

 cup, is formed of a large number of thin, discoidal joints. Calyx expanding upwards from 

 the basals, which are closely united into a thickened, discoidal piece without any visible 

 sutures, and but slightly wider than the upper stem-joints. First radials trapezoidal, and 

 united to form a rapidly expanding cup. Second and third (axillary) radials united 

 by trifascial articulation; the muscle-plates of the axillaries produced upwards into 

 strong, wing-like processes. Arm-joints (with the exception of the third, sixth, and 

 ninth) united in pairs by trifascial articulations, only the distal joint of each pair bearing 

 a pinnule, and there are no pinnules on the first few pairs. Interradial areas of the disk 

 naked, paved with loose anambulacral plates, or supported by a single oral plate. Am- 

 bulacra have covering plates, but no side plates. 



RemavTcs. — This genus was established by Sir Wyville Thomson in 1872 for a small 

 immature individual which was dredged at the mouth of the Bay of Biscay by the 

 "Porcupine " in 1869 from a depth of 2435 fathoms.^ But since the discovery by the 

 Challenger of adult examples of two much larger species in the Atlantic and Southern 

 Oceans, the original description of the genus requires modification. One of the Challenger 

 species {Bathycrinus aldrichianus) was described by Sir Wyville in the Journal of the 

 Linnean Society for 1876 ; but in the meantime a fourth species was discovered in the 

 North Atlantic by the Norwegian North Sea Expedition, and it was made the type of a 

 new genus Ilycrinus by Danielssen and Koren. ^ For it appeared to them to difi"er 

 chiefly in size and in the presence of pinnules from Bathycrinus, as described by Sir 

 Wyville from the immature " Porcupine " specimen ; and his amended account of the 

 genus, founded on the examples dredged by the Challenger, had not reached them in time 

 for reference. 



The nearest ally of Bathycrinus is undoubtedly Rhizocrinus. In fact, without an 

 acquaintance with this genus, one would hesitate to place Bathycrinus in the neighbour- 

 hood of the Apiocrinidse at all. There is but a very slight upward expansion of the stem 

 below the head and even in the ring of basals which rests upon it ; while the characters 

 of the radials are very difi'erent from those of Rhizocrinus and Bourgueticrinus. 



The general character of the dicebox-shaped stem -joints and of the branching root 

 is essentially the same as in Rhizocrinus. But the modes in which these joints are 



'■ Proc. Eoy. Soc. Edin., 1872, vol. vii. p. 772 ; see also The Depths of the Sea, p. 450. 

 2 Nyt Mag. f. Naturvidensk., Bd. isiii. p. 10. 



(ZOOL. OHALL. ESP. PART XXXII. 1884.) li 29 



