216 THE VOYAGE OP H.M.S. CHALLENGER. 



^uce of the more wcdge-sliaped brachials of a liolojnis-avm (PL III. figs. 10-12), but differ 

 in having the pinnule-socket at the base of the lateral process instead of on its upper edo-e. 

 Before the discovery of the support below the radials de Loriol considered Eudesi- 

 crinus to be a species of Eugeniacrinus ; and he still regards it as a member of the family 

 Eugeniacrinidse, to which he has also thought of transferring Cotylecrinus, though he 

 has never actually done so. This is partly due to his having been led to regard the 

 calyx-tube of IIolopus and Cyathidium as possibly composed of the five basal pieces 

 only/ though there are very serious objections to this view. We know also that the 

 Eugeniacrinidse, i.e., Eugeniacrinus, Phyllocrinus, and Tetracrinus, have a jointed stem, 

 which is not the case either in Eudesicrinus or in Cotylecrinus. Both these genera seem 

 to me to find their proper place in the family Holopidse, which I should characterise as 

 follows — Basals and radials closely united into a more or less tubular calyx of variable 

 depth. It is sessile and attached by a somewhat spreading base, the foundation of which 

 is probably formed by a dorsocentral plate, like that of Marsupites. Ten simple arms, 

 composed of a small number of massive joints. 



A. Radials high but asymmetrical, exhibiting a difference of bivium and trivium. 



a. Radials fused together with basals into a tubular body-chamber lodging the -viscera. 



A syzygy between the two outer radials, . . . . .1. Holoptts. 



/3. Visceral mass was probably lodged above the radials, which are mostly found 

 separated from the subjacent basals and the spreading base of attaehmeut. 

 A muscular joint between the two outer radials, . . . .2. Eudesicrinus. 



B. Radials apparently all alike. Two or more calyces sometimes associated as if budding. 



a. Radials and basals fused into a tubular body-chamber, . . . .3. Cyathidium. 



j3. Radials low, and readily separated from the basals and disk of attachment, . 4. Cotylecrinus. 



The remarkable Jurassic fossil, described by de Loriol as Gymnocrinus,^ is still too 

 imperfectly known to be placed in this family ; but I cannot help suspecting that it is 

 only a portion of the cup of a larger Crinoid. On the other hand, Micvo])ocrinus 

 gastaldii, described by Michelin^ from the Miocene of Superga near Turin, seems to be 

 closely allied to Holopus. Michelin's diagnosis runs as follows : " Radix expansa, non 

 ramosa, adhaerens, sublsevis ; corpus breve crassum, rotundatum, subpentagonale, exterius 

 granulosum, interius profundum, irregulariter vacuum ; margine revoluto in decern 

 segmentis acutis subdiviso." I am somewhat puzzled as to the identity of the ten 

 marginal segments. I do not think that they can represent the individual muscle-plates, 

 of which there would be ten in a decalcified calyx ; nor does it seem likely that 

 Micropocrinus is a ten-rayed type like Promachocrinus {ante, pp. 37, 38). The real 

 nature of this Crinoid must therefore remain undecided for the present. 



On the other hand, the Palaeozoic Edriocrinus, which has been described by Hall 



1 Paleont. Frang., he. cit., p. 191. ^ Hid., p. 209, 



2 Description d'un nouveau genre de la Faniille de Crinoides, Eev. et Mag. ZooL, ser. 2, t. iii. p. 93. 



