XI. Balanocrinus. 397 



It seems probable that there was rarely a long succession 

 of whorls with only two cirri^ still less with only one, but 

 that the succession was 2:2:3. Considering the fairly 

 large proportion of specimens with whorls of tliree in our 

 material, it is strange that that number should not have 

 been noted by previous writers. Dom Aurelien Yalette, in 

 his letter of 1-4 September, 1916, does, however, say " deux 

 ou trois tout au plus." 



Quenstedt (1878, ' Encriniden,' p. 268, pi. xcix. fig. 170) 

 gave the name Pentacrinus tridactylus to a stem-fragment 

 from Tertiary beds near Castellane in S. France because 

 there were 3 cirrus-facets opposed at the node. This, how- 

 ever, seems from the figure to be an Isucrinus. 



Tlie preceding facts fully bear out the anticipation of 

 P. H. Carpenter in his description of Peyitacrinus alter ni- 

 cirrus (1884, ' Challenger Rep., Stalked Criuoids,' pp. 322, 

 323), which is referred by A. H. Clark to his Endoxocrinvs. 

 In that species there is a regular alternation of 2 with 3 cirri 

 to the whorl, as '• the leaves on the stem of a Labiate plant." 

 Only one irregularity was noted in the whole 147 nodes 

 examined : in one stem the seventh and eighth nodes both 

 bore 3 cirri in such a position that one cirrus fell on the 

 same radius in both whorls. Carpenter mentioned the 

 reduction of cirri to two in Pentacrinus bronni Hagenow 

 (which is a Balanocrinus), and P. didactylus, and to three in 

 P. tridactylus, and suggested that " if longer pieces of these 

 stems were known they might show the same regular alter- 

 nation in the positions of the successive cirrus-whorls which 

 is so striking in Pentacrinus alternicirrus.^^ 



Neither in his published writings nor in his letters tJ me 

 on this subject did Carpenter suggest any cause for this 

 remarkable peculiarity, and the matter has since remained 

 where he left it.^ 



We turn now to the similar specimens from the London 

 Clay. Concerning them the main questions to be answered 

 are : What is their generic position? Do they include more 

 than one species ? Are any or all of them conspecitic with 

 any of the foreign specimens ? The answers to these 

 questions are given in the following Synonymy : — 



Balanocrinus sulbasaltiformis. 



"x d 58. Entrochus-Asteriae, from a Brick Clay-pit, on the South- 

 side of Islington.'" 



" X d 59, GO. Entrocho-Asteriae, found in the Tile Clay-pit behind 

 Trinity-Chajjel, at the end oi Bondstreet, St. James's." 



