﻿23O SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 47 



Ambulacra angularly elevated, prominent, extending- around the 

 entire periphery of the theca, and touching the column in specimens 

 20 mm. or more in length. In some of these mature specimens the 

 ambulacra, when near the column, are deflected, and one or both will 



pass on the same side for 

 a short distance in front 

 of it. In smaller speci- 

 mens the ambulacra do 

 not 'quite reach the col- 

 umn, and in one having a 

 thecal length of 15 mm. 

 they stop within 3 mm. of 

 the stalk. In the largest 



Fig. 29. — Analysis of Pscudocrinites gordoni 



c h 1 specimen there are 40 



brachioles on each side of 

 an ambulacrum, while in one having a thecal length of 15 mm. there 

 are about 21. Length of brachioles not definitely known; those of 

 the apical region not less than 11 mm., stout, and with about 17 

 pieces in each column. Ambulacral groove wide and covered by a 

 complex series of small and large ambulacralia arranged as shown 

 in figure 1 1 of plate xxxix. 



Basal pectinirhomb smallest, in the largest specimen having about 

 80 grooves; that on plates 12 and 18 has about 90, and the one on 

 plates 14 and 15 is the largest, with about 120. 



Hydropore minute, closely adjoining the madreporite. 



Anal pyramid depressed, consisting of 7 somewhat ornamented 

 plates surrounded by a circle of 8 larger plates of irregular size and 

 definite sculpture. 



Column slender. Length unknown. 



Comparisons. — P. gordoni is the most prolific of American Pscu- 

 docrinites. The nearly circular outline of the theca and the greater 

 number of brachioles distinguish this species from P. clarki and P. 

 perdewi. Of forms with nearly circular theca P. stcllatus differs in 

 the very prominent sculpturing and the smaller number of brachioles, 

 while P. claypolei differs in the vermiform sculpturing and fewer 

 brachioles, 



P. gordoni undergoes but little modification in form. In general 

 the outline is circular, but occasionally a specimen is a little more 

 elongate and in rare cases one is more transverse. Of the latter, one 

 has a thecal length of 29 mm. ; breadth 33 mm. ; and depth 19 mm. 

 There is very little abnormal material. One specimen has the ambu- 

 lacrum R IV abutting against the lower pectinirhomb instead of 



