REPORT ON THE CRINOIDEA, 237 



The nearest, and in fact the only ally of Bathyci'inus is Rhizocrimis ; but the 

 differences between the two genera are much greater than their resemblances. The latter 

 may be summarised as follows : — 1. The bifascial union of the stem-joints. This is 

 common to Bourguetici'inus and Mesocriims, to the Pentacrinoid larva of Comatula, and 

 the Palseozoic Platycriniis. 2. The presence of large processes on the second joints above 

 the radials, which support the disk. 3. The absence of pinnules from the lower parts of 

 the arms, and the union of the arm-joints in pairs, with a pinnule on the second joint of 

 each pair only. 



The differences between the two types are shown in the following Scheme. 



Rh kocrinus. Bathycrinus. 



a. May have radicular ciiri. a. No radicular cirri. 



b. Only one or two discoidal joints at the top of b. Many thin discoidal joints at the top of the 



the stem, and those not very thin. stem. 



c. Basals long; radials short, and very closely c. Basals short; radials long, and comparatively 



united. free. 



d. Primary interradial cords fork within the d. Primary intenvadial cords fork within the 



basals. sutures between the radials. 



e. Five arms. e. Ten arms. 



/. All the joints above the first radials are united /. The fifth, eighth, and eleventh joints above the 

 in successive pairs by syzygy. primary radials have a muscular articulation 



at each end ; the remainder are united in pairs 

 by trifascial articulations. 

 g. The first pinnule may be either on the g. The first pinnule not lower than the eleventh 

 primitive sixth or eighth joint above the first joint above the first radial, 



radial, i.e., on the epizygal of the third or 

 fourth syzygial pau-. 



It has been already pointed out that Bathycrinus ranges through a greater number 

 of degrees of latitude than any other Stalked Crinoid, even Rhizocrinus ; and it is only 

 surpassed in this respect by the ubiquitous Antedon. Bathycrin.ts carpenteri was 

 found by the Norwegian North Sea Expedition as far north as 65° 55' N. lat. ; 

 w]iU.e Bathyc7'inus aldrichimius was twice met with by the Challenger in the Southern 

 Ocean beyond the parallel of 46° S. lat. In the intervening Atlantic Ocean have been 

 found Bathycrinus gracilis (Bay of Biscay) and Bathycrinus campbellianus (just north 

 of the equator) ; while other examples of the genus, the specific characters of which are 

 as yet unknown, were dredged by the "Talisman" in the Atlantic (1883) at a depth of from 

 2000 to 2380 metres (1200 fathoms).^ It is distinctly an abyssal type, ranging from 

 1050 to 2435 fathoms. The only Crinoids which have been found at greater depths than 

 the latter are two species of Antedon. 



We have no certain knowledge of the occurrence of Bathycrinus in the fossil state ; 

 though it is by no means impossible that some of the stem- joints so common in the 



• Rapport priliminau'e sur I'expedition du " Talisman " dans I'Ocean Atlantique, Comptes rendus, t. xcvii. 

 p. 1392. 



