192 MR. P. H. CARPENTER ON THE GENUS SOLANOCRINXJS 



the five that are situated interradially are the strongest (PL IX. 

 fig. 1). Resting on their summits there appear the rounded ends 

 of the prismatic basals that intervene between the lower angles 

 o£ the radials and the upper surface of the centrodorsal. The 

 distal faces of the radials do not rise directly from the margin of the 

 centrodorsal, as in most recent Comatulce ; but they are separated 

 from it by a portion of their dorsal surface that appears exter- 

 nally, as in Pentacrinus (PI. XI. figs. 21 a, 23 a). I have else- 

 where* called this the "outer dorsal surface," in contradistinction 

 to the " inner dorsal surface," that rests on the centrodorsal piece. 

 The distal articular faces have a considerable slope inwards to- 

 wards the vertical axis of the calyx, and have very distinct inter- 

 muscular notches in the middle of their upper borders that lead 

 into the corresponding furrows of the ventral faces. There are 

 also distinct interradial notches between the muscle-plates of 

 every two adjacent radials, which are continuous with the ventral 

 interradial furrows on the upper surface of the calyx. 



A careful study of several specimens commonly referred to this 

 type has shown me, not only that it exhibits a great amount of 

 variation within what may fairly be regarded as specific limits, 

 but also that many forms have been referred to it which differ 

 from it in several points. Many of these differences are of the 

 same nature as those which exist between the corresponding parts 

 of various recent Comatulce, and are always accompanied by varia- 

 tions in other characters that necessarily remain unknown for 

 the fossil forms. The shape and relative proportions of the 

 centrodorsal and radials vary considerably among the different 

 species of recent Comatula (PI. XII.) ; and one seems justified in 

 concluding that variations of a similar character among the fossil 

 forms may be taken as indicative of specific differences. In this 

 way I hope to show that the Comatula-l'nimEL of the White Jura 

 of Wurtemburg was considerably more varied than has hitherto 

 been supposed. 



I have never seen any specimen of Solanocrinus precisely like 

 the type of S. costatus (=Antedon costata, PI. IX. fig. 1). There 

 are, however, three specimens in the Woodwardian Museum and 

 one in the British Museum, all from Nattheim, that resemble 

 it very closely. Apart from irregularities in the development 



* " Preliminary Report upon the Comatulce of the ' Challenger' Expedition,'* 

 Proc. Roy. Soc. No. 194, 1879, p. 392. 



