40 rLATVCRINID^E. PLATYCRINUS. 



10. Species. Platycrinus Rugosus. (Miller.) 

 PL IV. fig. 2. d, to h. 



Definition. — Dorso-central plate pentagonal and massive ; perisomlc plates tumid ; 

 abdominal plates irregularly hexagonal ; mouth unobtrusive. Ra\s thirty ; column 

 round at its attachment to the body, but elliptical as it recedes from it. All <he plates 

 are boldly tuberculated. 



Synonymes and References. 



Pentacrinites. — Cumberland Trans. Geol. Soc. vol. 5, PI. IV. fig. 4 and 5. 

 Platycrinites rugosus. — Mill. Crinoidea, p. 79. 



Pliill. Geol. York. PI. II. fig. 20, p. 204. 



Aust. Ann. ^ Mag. Nal. Hist. vol. 10, p. 109. 



Portlock. Geol. Rep. 1843. 



Blainv. Man. U Actin. PI. XXIX. fig. 4. 



Formation and Localities. 



Carboniferous limestone. — WhitewcU in Bolland ; Caldy Island, on the south 

 coast of Wales; the Mendip Hills; Lancashire; Leigh Downs, near Clifton; Black 

 Rock, Avon side ; and Hook Point, Wexford. 



Description of the Calcareous Frame Work. 



The Dor?o-central Plate — Is in this species generally very flat and thick, 

 with a few elongated tubercles irregularly arranged on its surface. Miller has 

 fallen into the same error with respect to the dorso-central plate of this Platycrinus as 

 he has with others of the genus. — The furrows or grooves alluded to at page 7. are deeper 

 in the dorso-central plate of this species than in others of the genus. 



The Perisomic Plates— Are thick and tuberculated; in some specimens the 

 tubercles are arranged with considerable regularity, in others they are scattered without 

 much regard to form. The excavations for the attachment of the rays are deep but 

 rather narrow. The structures of tliesc and the dorso-central plate are sulcated. 



