POTERIOCRINID^. — POTERIOCRINUS. 69 



There has been much uncertainty as to whether the dorso-central plate of Poterlocrimis 

 is tripartite, orquinquepartite, and even yet some doubt may remain on the subject, though 

 the general evidence is in favour of its tripartite arrangement. Miller in his work on the 

 erinoidea has represented that which is probably the first series of petisomiq plates, as 

 the dorso-central plate (pelvis). But it is just to remark that he did so with considerable 

 hesitation, owing to the difficulty he experienced in obtaining specimens shewing the 

 connexion between the plates of the body and the first columnar joint, 



Professor Phillips represents the dorso-central plate as tripartite, in which opinion 

 after a careful examination of many specimens we are inclined to coincide. 



1. Species. Poteriocrinus Crassus. (Miller.) 

 PL VIII. fig. 3, a to. m. and PL IX. fig. 1. 



Definition. — Dorso-central plate tripartite?; first series of perisomic plates, five; 

 ray-bearing plates five; intermediate lateral plates two, or three ; mouth centrical, much 

 elongated and tubular, 



Synonymes and References. 



Poteriocrinites crassus. — Mill. Nat. Hist. Crin. p. 68. 

 Encrinites crassus. — -Schloth. Nacht. t. 25. /. 2. 

 Poteriocrinites crassus. — Blainv. Man. d" Act. 



M. Edw. ap. Lamk.U, p. 664. 



Munst. Beitr zur Petref. 



M de Koninck. Descrip. des Ani. Foss. PL F,fig. 4. 



Flem. Brit. Anim. p. 495 



Woodward, Cat. of For. foss. 



Cumberl. Tran. of the GeoL Sac. of London. Vol. 5. pi. ■}. J'. 2. 

 page 90. (\st series) 



Formation and Localities. 



Carbonifereous limestone, Yorkshire ; banks of the Avon, Bristol ; Hook Point, 

 Wexford ; Arran ; and Tournay. 



Magnesian beds of the carboniferous limestone, Clevedon Bay, Somersetshire. 

 Dr. Woodward has stated that this species occurs in Syria. 



