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



tlicy miglit then liave been lost after the decay of the perisome uniting them. Those of 

 Holojnis were retained in the dry specimen which was figured by Pourtalfes,^ and 

 subsequently by Sir Wyville Thomson ; and the condition of the Palasozoic Coccocrinus 

 seems to me to be entirely explained by that of the recent Holopus. 



Wachsmuth and Springer^ describe it as follows : — " In well preserved specimens of 

 Coccocrinus, the vault is constructed of five large oral plates, which rest upon five 

 interradial pieces. The oral plates are not in contact laterally, but leave five slits, which 

 in the fossil have no floor nor covering, and leave an open space in the centre." They 

 are strikingly similar to the orals of the recent Hyocrinus (PI. VI. figs. 1-4), as has been 

 pointed out by Zittel ; and the resemblance to the orals of Holopus (PI. III. fig. 2) is still 

 greater, as the latter rest directly against the calyx plates, which is not the case in 

 Hyocnnus. In both the recent forms and also in Thaumatocrinus (PL LVI. fig. 5) the 

 clefts between the triangular oral plates are open and uncovered, as in Coccocrinus. 

 Schultze^ follows Eoemer in thinking that these slits do not penetrate into the cavity of 

 the calyx ; Ijut that they were hollows for the reception of the arm bases, as in 

 Eucalyptocrinus. But Wachsmuth, having examined Schultze's specimens, states 

 distinctly that these grooves have no floor. He says in the Revision (part ii. p. 17) that 

 '■' the similarity to Hyocrinus is probably merely superficial, as the lateral grooves in 

 Coccocrinus were evidently {why ?) closed by additional plates as in other Platycrinidse, 

 while they are open in Hyocrinus." Again "it is evident that the central space and 

 open furrows were covered in the animal as in similar genera." The oral plates " do not 

 join laterally nor in the centre, but leave a median space and lateral shts, which in perfect 

 specimens were doubtless closed, the one by the apical dome plates and the slits by small 

 marginal pieces." . ..." In Coccocrinus a covering of the ambulacral groove has not 

 yet been observed, but, judging from the fissure between the oral plates, it probably rested 

 just upon their edges, and formed an intermediate link between the vault structure of 

 the Cyathocrinidse and Platycrinidse."* 



When Wachsmuth wrote the passages which have been quoted above, he held, like 

 Zittel and myself, that the five large triangular plates which rest on the primary inter- 

 radials of the calyx are homologous with the orals of recent Crinoids. He has since, 

 however, come to the conclusion that " Coccocrinus had externally no oral plates, its so- 

 called orals are secondary interradials, and mouth and food-grooves were covered by 

 supra-oral plates " (Extract from Letter). I must confess that I greatly doubt the 

 existence of this additional covering in Coccocrinus, which seems to Wachsmuth so 

 evident ; for I find it difficult to believe that the " Scheitelstiicke," as Schultze called 

 them, are not oral plates like those of the Neocrinoids. It is of course possible that their 

 resemblance to the orals of Holoinis, Hyocrinus, and Hiaumatocrinus is simply an 



1 Hassler Crinoids, pi. x. fig. 9. ° Revision, part ii. pp. 17, 58. 



5 Op. cit., p. 89. * Revision, part ii. pp. 17, 30, 58, 59. 



