248 



PROFESSOR ALLMAN ON A PRE-BRACHIAL STAGE 



arms in Cupressocrinus. The following diagram, fig. 2, exhibiting an analysis of 

 Haplocrinus, will render the relations here insisted on more apparent. 



Fig. 2. Again, in the singular Devonian crinoid 



Coccocrinus, J. Miller, we have the roof in the 

 form of a depressed pyramid, composed chiefly 

 of five large pointed pieces, whose apices meet 

 in the centre, and which are also plainly inter- 

 radialia and homologous with the sides of the 

 pyramid M'hich forms the roof in IIiq)hjcrinus, 

 and in our larval Comatula, while five smaller 

 pieces, constituting a first series of inter-radialia, 

 are associated with them, as may be seen in the 

 annexed diagram, fig. 3. 



In the genus Stephanocrinus (woodcut, fig. 4), 

 if we adopt the analysis given by J. Hall,* 

 who has had abundant opportunities of studying 

 this crinoid in the Silurian strata of the United 

 States, the inter-radialia will be represented by 

 the small triangular plates whose apical angles meet in the central point of the 

 roof, and by the large plates which meet the bases of these, and have their 



sides prolonged vertically as five strong pyra- 

 midal spines which surround the margin of the 

 roof, and give its characteristic crown-like form 

 to this elegant little fossil ; while the calyx 

 will consist of a zone of three basalia, followed 

 b}' a zone of five large radialia, which support 

 the five small semicircular plates occupying the 

 margin of the roof, and constituting a zone of 

 distal radialia. The roof itself is completed by 

 five pairs of long narrow parallel plates which 

 alternate with the inter-radialia, and which 

 must be regarded as axillaryf plates. If, how- 

 ever, with RoMER we view the spine-like plates, 

 not as distinct elements, but as formed by 

 the prolonged angles of two contiguous radialia, 

 then the inter-radialia will be represented by 



Plan of Haplocrinus. 

 L Basalia, ... 5 



2. Radialia, . . . 3x2 + 2x1 



3. Inter-radialia, . 5 



Fipr. 3. 



Plan of Coccocrimis. 



1. Basalia 3 



2. Radialia 5x2 



3. Inter-radialia, . . 5x2 



the five small triangular apical plates alone, t 



* Pala?ontology of New York. 



f The terra " axillary" is here used in the sense in which it is employed by de Koninck. 



J I cannot, with Romer, Pictet, and Bronn, regard Stephanocrinus as a cystidian, a view 

 opposed not only by the numerical law of its parts, but by the structure of its roof, and the position 

 of its arms as determined by Hall, from which we must infer a considerable development for the 



