70 F. A. BATHER, CRINOIDEA OF GOTLAND. 



between the large axillaries of the arms (Pl. IV, tig. 127), and tliis confirms the idea that 

 the basi-radial hinge is a muscular articulation. These plates nia}- be compared with the 

 patelloid plates of the Articulata and with similar interstitial plates in other Crinoids, and 

 they are in no way to be considered as fragments of an integument. It is possible that 

 Dr. Ringueberg has confused thein with some other appearance. 



Although no such strueture has hitherto been described outside the genus Euckiro^ 

 crinus, there can be little doubt but that it is eommon to all Calceocrinidae, though per- 

 haps variously developed in the different species. In many cases too zealous eleaning of 

 the specimen must have destroyed what only eseaped notice because attention had not 

 been directed to it. Sinee seeing the unmistakeable appearance of the Klinteberg specimen, 

 I have found many traces of these plates in other forms. Thus, fragments of 5 such 

 plates reniain in the speeimens of C. fureillatus in the British Museum [E. B001], 1 in 

 the type of C. gotlandicus, a few in speeimens of C. pugil, more obscure remains of some 

 such strueture in the types of C. tucanus and C. tenax, a few in various English speei- 

 mens of species as yet uncertain, at Cambridge and in the British Museum, and many 

 well preserved in the specimen of Halysiocrinus ventricosus in the Riksmuseum (Plate IV, 

 tig. 142). 



4. Ventral surface. Messrs Wachsmuth and Springer 1 ) say, »There are besides 

 suramit and vault pieces which, however, were not described by Hall». For this one 

 might now substitute: »There are probably snmmit or vault pieces (tegminal plates), but 

 none were described by Messrs Wachsmuth and Springer». Dr. Ringueberg has used the 

 term vault» in his description of »Proclivocrinus* (op. rit., p. 397) and P. ( — Euchiro- 

 i- rin iis) radiculus (op. rit., p. 400); but, even with the aid of his tigure (Pl. X, tig. 13 n), 

 it is difficult to understand his description, which leaves it doubtful whether the strueture 

 described be »convex» or »concave». It would appeär, however, that the four plates which 

 form the greater part of the cup, viz., the T-piece, the anterior radial, the left posterior 

 radial, and the lower half of the left anterior radial, each give off a process on their inner 

 side, which processes appear to start from the lower part of the plates and are described 

 as meeting in the centre. Whatever the strueture may be, it agrees neither in situation, 

 nor orientation, nor eomposition, with any strueture that any writer has hitherto called a 

 »vault», a »tegmen», a »disc», or any such name in any Crinoid or in any Pelmatozoan 

 whatsoever. The very few speeimens of Calceocrinus available for dissection present no 

 trace of such a strueture as shown in Dr. Ringueberg's remarkable drawing; it may 

 possibly be an exageration of the peculiar constriction of the lower part of the calycal 

 cavity that obtains in Pisocrinus pilula and P. ollula (Pl. I, tigs. 11, 17). The artieular 

 surfaces of the radials as tigured for Calceocrinus stigmatus 2 ) present a close resemblance 

 to those of Pisocrinus and allied forms. A specimen of 6'. pugil, in which the cup has 

 been broken off just below the arms, shows that the actual ventral opening of the cup 

 Avas very small, sinee the muscle-plates of the radials close in on every side, and that this 

 opening was ehiefly covered by the plates of the ventral tube; it therefore seems probable 



>) Revision III, '275, Proc. L886, p. 1 '.»',). 



-) J. Hall, 28th Rep. N. V. State Cab. Nat. Ilist. Pl. \i\. ti ti . 10, 1879, and Ringdeberg, !<>,■. rit. 



