MORPHOLOGICAL PART. 61 



tion toward the proximal ring of plates visible in the calyx as that of Milleri- 

 crinus and Apiocriniis, except that in the two latter the space above the top 

 stem joint is vacant, while in GrapJdocrinus it is filled by very small infrabasals 

 (compare Fig. 17 with Fig. 20 on Table A). 



Small infrabasals are known to exist in the base of the Pentacrinoid genus 

 Extracrinus, and de Loriol has discovered similar plates in two species of 

 MiUericrinus (Plate VI. Figs. 1 a, h, and 2 a, h). Those of 3£. folydadylus he 

 describes as follows : * ^' Je distingue tres nettement, sur deux individus, 

 cinq pieces extremement petites, a peine distinctes a I'oeil nu^ qui sont 

 logees au centre de I'article basal; chacune reposant sur le sommet de Tune 

 des carenes, dans une direction radiale, au centre se trouve, une petite 

 depression qui forme le fond de la cavite. Ces petites pieces, que je 

 n'avais jamais encore observees, jouent evidemment le role de pieces infra- 

 basales, mais a I'etat tout a fait rudimentaire." Similar pieces were dis- 

 covered by him in his M. Orhignt/i, of which he says : t '' Files ne peuvent 

 absolument se voir que lorsque, par un hasard heureux, I'article basal peut 

 se degager du calice. II me parait indubitable que se sont la de petites 

 pieces infrabasales rudimentaires semblables a celles que j'ai signalees dans 

 le M. poll/ dady his r 



Admitting these plates to be infrabasals, it is certainly quite improbable 

 that other species of MiUericrinus having a pentangular stem, and those with 

 a round stem, and the species of Apiocrinus, — a genus which, according to de 

 Loriol, is very closely allied to MiUericrinus and Giiettardicrinns — should have 

 possessed no infrabasals. In all species of MiUericrinus, the column, unless 

 it is round, has interradial angles (Plate YL Figs. 1"*, 3, 4^, 5), exactly as in 

 M. Orlignyi and all dicyclic Palaeocrinoids \ and hence, if the genus were not 

 dicyclic, this structure would be at variance wath that of other Crinoids. We 

 come to the same result if we examine the vacant space within the basal 

 ring. This is radial, and disproportionate in size to the axial canal of the 

 stem, which is small and circular ; whereas if it represented the axial canal 

 of a monocyclic Crinoid it should be interradial. The space is large enough 

 to have contained, besides the canal, additional plates, which, if present, 

 would have occupied the same position as the infrabasals of M. OrUgnyi, 



The column of dicyclic Crinoids abuts either entirely against the infra- 

 basals, or partly also against the basals. The latter is the case with the top 



* Paleont. Prang., l''^ serie, Animaux Livertebres, Terr. Jurassic, Tome XL Premiere Partie, Crinoides, 

 Paris, 1882-1884 p. 553, Plate 110. Figs. ] and 2. 

 t Ibid., p. 566 (Plate 116, Pig. 1, b, c, d). 



