﻿SCHUCHERT] SILURIC AND IMA (i.\l( CYSTIDEA 233 



Ambulacra well defined, flat Lopped, extending around the entire 

 periphery of the theca and touching the column. Ambulacrals 

 large. Each ambulacrum in full-grown specimens has about 36 

 brachioles ; in a small specimen having a thecal length of 15 mm., 

 there are hut 24 hraclholes. Brachioles usually not preserved. 

 Ambulacral groove wide, roofed by a median double row of tiny 

 angular amhulacralia arranged in short crescents, and outside of these 

 h\ a single row of much larger, strongly elevated plates, each one of 

 which is as large as two of the ambulacrals. For detailed structure, 

 see figure 7, plate xxxix. 



Basal pectinirhomb with aboul 60 dichopores, that of plates i_> and 

 18 with 80, and of 14 and 15 with 90. 



Madreporite quite large for Pseudocrinites, hut the hydropore is 

 exceedingly minute. 



Anal area small, composed of 2 circles of plates ; the outer has 7 

 nodose pieces and the inner depressed pyramid has the same number 

 of plates. 



Column slender, hut its length is unknown. 



Comparisons. — This species is readily distinguished from all other 

 Pseudocrinites by the strongly stellate sculpturing of the plates. P. 

 gordoni differs further in having many more brachioles. 



Formation and locality. — Of this species three specimens are in the 

 U. S. National Museum, seven in Mr. Hartley's collection, and two in 

 Mr. Gordon's. All are from the quarries near Keyser, West Vir- 

 ginia. 



Cat. number 35,069, U. S. N. M. 



PSEUDOCRINITES CLARKI Schuchert 



(Plate XXXVI, figures 4-7; Plate XXXIX, figure 14) 



Pseudocrinites clarki Schuchert, Amer. Geol., xxxn, 1903, p. 237. 



Length of largest theca 44 mm. ; greatest width 30 mm. ; depth 

 22 mm. Length of an average specimen 30 mm. ; greatest width 22 

 mm.; depth about 16 mm. For general form, shape of plates and 

 their ornamentation, see figures 4-6, plate xxxvi. 



Ambulacra in mature specimens very prominent, triangular in 

 transverse section, extending around the entire periphery of the theca 

 and touching the column. In the second largest individual each 

 ambulacrum had about 44 brachioles, in another mature but smaller 

 specimen there were only 32. Brachioles unknown, apparently more 

 slender than in P. gordoni. Ambulacral grooves narrow, and cov- 

 ered by highly elevated amhulacralia of about the same nature as in 

 P. gordoni, hut less numerous and the larger plates more nodose. 



