6(5 THE A'^OYAGE OF H.M.S. CHALLENGER. 



plates ou the arms of Gissocrinus, which he described in his generic diagnosis^ as 

 " pinnulse brevissimse verrucseformes." They do not correspond to the " assulse ambula- 

 crales " of Gissocrinus ; for these, as pointed out by Wachsmuth and Sjjringer,^ are the 

 joints of the arm-bases which are recumbent upon the vault, being raised above the 

 general level, and " covered by small alternating plates like the fi'ce arms." 



Thus, then, the expression " pinnulse " was used by Angelin for three diflerent types of 

 structure in Hahrocrinus, Crotalocrinus, and Gissocrinus respectively. The first of these 

 represent tlie true pinnules of recent Crinoids ; while, as was first recognised by Zittel,"' 

 the plates on the arms of Gissocrinus represent the " Saumplattchen " which Miiller had 

 described on the ambulacra of Pentacrinus. He takes the same view of the plates which 

 Angelin called "rudimenta, pinnularum semiglobosa" in Cyathocrimis ramosus. The 

 corresponding plates in Cijathocriims longimanus have indistinct cross markings ; and 

 Messrs. Wachsmuth and Springer have interjareted this as indicative of segmentation into 

 pinnule-joints ;* for they speak positively of " two rows of five successive plates each, one 

 row being given off' from the right, the other from the left side of the furrow, and perfectly 

 covering it." The arms of Cyathocrimis, however, are only single-jointed ; and they 

 state elsewhere ' that " in doul)le-jointed arms every joint at each side bears a pinnule, 

 while in those with single joints the pinnules are found only on alternate sides." But 

 Angelin's figures show that on five arm-joints there are twelve of these rudimentary 

 pinnules, six on each side, while in Gissocrinus there are from four to six ou each arm- 

 joint. In spite of these facts, however, Wachsmuth and Springer give it as their opinion 

 that these plates which cover in the ambulacral groove in the arms are the homologues of 

 the pinnules, though too rudimentary to be ranked as such.^ [See p. 84.] 



The chief point of their position (and they make ithe most of it) is the apparent 

 segmentation of the " rudimentary pinnules " into five joints, as shown in Angelin's 

 figures of Cyathocrinus longimanus. It would be very desirable if this could be verified 

 on the actual specimens. The presence of two rows on each side of the ambulacrum in 

 Oyathocrinus, Gissocrinus, &c. , is nothing unusual ; for they represent the side plates and 

 covering plates of Neocrinoids, of which there may be from five to seven to one arm-joint. 

 Precisely similar plates occur on the pinnules as well as on the arms ; and they also form 

 part of the skeleton round the radiating tubes beneath the vault of Actinocrinus " whicli 

 connect with the ambulacral furroM's in the arms." '^ But I think that Wachsmuth and 

 Springer would hesitate before considering the two upper rows of plates in these radiating 

 tubes as "rudimentary pinnulfe." 



^ Iconograpliia Crinoirleorum, p. in. - Revision, part ii. p. 91. ^ PaUt'ontologiL', pp. 338, 354. 



* Revision, part i. pp. 24, 82. ^ V'id., part ii. p. 24. " Ihid., part i. p. 82. ' Ihirl, part ii. p. 28. 



