﻿SCHUCHERTj SILURIC AND DEVONIC CYSTIDEA 22/ 



Pseudocrinus Haeckel, Die Amphorideen und Cystoideen, Beitr. Morph. 

 u. Phyl. (1. Echinodermen, Leipzig, [896, p. 135. Bather, Treatise 

 on Zoology, in, Echinoderma, London, [900, p. 62, fig. 29. 



The Cystidea were not separated from other Echinoderma until 

 iS) |, by von Buch; a year earlier, however, Pearce defined the genus 

 / seudocrinites as follows : 



Mr. Pearce regards them as constituting a new genus which he- 

 proposes to name P seudocrinites, including two species both having 

 the arms [ambulacra] and lingers [brachioles] inserted in hands, 

 which commence just above the column and pass over the plates of 

 the head to its summit. The one form has two [now accepted as 

 the genotype], the other four ranges of fingers [Staurocystis]. 

 They resemble each other in having the columns at their superior 

 part composed of rings, gradually increasing in size towards the 

 head. The plates of the head are thin and broad, and marked on 

 their outer surface by lines of growth, and radiating ridges resem- 

 bling the plates of the marsupite. They are also furnished with four 

 orifices [pectinirhombs. Seeing two on one side he concluded there 

 were four in all, but there are only three] of a lozenge shape, most 

 singularly inserted in the plates of the head, and their arms and 

 fingers are exceedingly short. The fingers [brachioles] are com- 

 posed of two rows of bones [plates], each bone on the one side being 

 inserted between two of the opposite. These fingers appear to be 

 placed in four rows [should be two rows on each ambulacrum] on 

 each of the hands, and pass off from the head in a radiating direc- 

 tion, commencing at the column and uniting at the summit. Mr. 

 Pearce names the first species F 'seudocrinites bifasciatus [the geno- 

 type selected by Haeckel] , and the second P. quadrifasciatus [selected 

 by Haeckel as the genotype of Staurocystis] ." 



Emended definition of P seudocrinites. — Staurocystinas with the 

 sides of the theca compressed, varying in outline from circular to 

 elongate subquadrate, and composed of 19 plates. These are ar- 

 ranged as follows : 



Basal row has plates 4, 1, 2, 3. 



Second row has plates 5, 6, 7, 8, 9. 



Third row has plates 10, n, 12, 14. 



Fourth row has plates 16, 17, 18, 13, 19, 15. 



Fifth row has deltoid 23. 



Deltoid 23 is very small, situated between the ambulacra on the 

 left oral side of plate 18, with the hydropore and madreporite present. 

 Hydropore closed by a pyramid of 5 plates. Anal area small, placed 

 between plates 7, 8, 13, and 14, and consisting of an outer complete 



