68 F. A. BATHER, CRINOIPEA QF GOTLAM). 



basal (1. post. B and 1. ant. B) just enters into the facet and is .scen as a small triangulär 

 space al one end of the above-mentioned suture-linc. At the o.ther end of this suture- 

 line, in the righl posterior interradius, is a similar triangle, not very easy to distinguish 

 al first, hut, when once seeu, clearly visible to the naked eye. The facet is concave, hut 

 the concavity is not regular; on the contrary, each plate that enters into the facet slopes 

 down towards the axial canal, so that there are 4 distinct surfaces lving at different 

 angles. When this fact has been appreciated it is still niore easy to see the small trian- 

 gulär plate lying in the right posterior interradius. This plate ean represent nothing hut 

 the 5th basal, and its discovery proves the correctness of opinions come to, on a priori 

 grounds, long before its existence was known. 



2. The Hinge. The description of Calceocrinus given by Wachsmuth and Sprin- 

 ger appears to have been based on a study of Carboniferous species, which probably 

 belong to the genus Halysiocrinus {ri</<- supra); it cannot therefore be taken as a descrip- 

 tion of Calceocrinus s. *tr. A few of their remarks, however, may be noticed, since they 

 apply equally to the whole of the family. The description given by these authors J ) of 

 the articulating surface between basals and radials un the left anterior face of the cup 

 differs from that given by Ringueberg, in that they mention a- small axial canal. If I 

 understand their language aright, the articular margin of the left anterior inferradial is 

 excavated by a deep fossa; the articular margin of the coinbined left anterior and left 

 posterior basals is excavated by a shallower fossa; the extreme edges of the plates, where 

 they meet one another, form a narrow ridge between the two fosste; in the middle of the 

 fossa belonging to the left anterior radial there is a triangulär projection from this ridge; 

 in this projection is the axial canal. No European specimen yet found shows either the 

 triangulär projection or the axial canal. 



Both Wachsmuth and Springer and Ringuebekg consider that the fossa 1 were for 

 the reception of »elastic ligament». Ringueberg further says: »The posterior curved margin 

 [se. of the base] was not attached directly to the arch into which it fits [composed of the 

 upper and lower halves of the right posterior and right anterior radials and parts of the 

 large radials], hut was united by means of soine elastic and flexible medium, which 

 allowed a considerable degree of separation at this point»; and from his plate XI, figs. 4 <i, 

 4 />, we learn that, in Dr. Ringuebekg's opinion, the base of ■»Pröclivocrinus was united 

 to the internal projections of the radials [_Qy. what he elsewhere calls the »vault»] by 

 »muscles which held the calyx down». The frequent occurrence of bases apart from the 

 rest of the cup, and the anchylosis of the basals to one another, and of the radials to one 

 another, conhrm the idea that the base formed a support on which the rest of the calyx 

 moved. It is not likely, however, that the angular motion was verv givat: the column 

 itself is usually found curved at its proximal end, and could doubtless be somewhat 

 straightene.d: 'he articulatioiis betweeja the radials and the arms were, as Wachsmuth and 

 SrKiNGER have noted, »widely gaping», and this was often the case between succeeding 

 arm-ossicles; so that the arms themselves would lie coiisidcrahly raised and expanded hy 

 the contracfion of their own muscles. Wachsmuth and Springek mention a specimen in 



') Kr^. Ill, -27'.), Proc. Ig86 3 p. 203. 



