SILURIAN RADIATA. 163 



for mm g a distinct siphon ; outer wall extremely thin, forming 

 a few root-like tubercles on the conical young ; terminal cup 

 with a depressed flattened centre and very convex outer area. 



In the Wenlock limestone of Wenlock. 

 (Col. University of Cambridge.) 



Clisiophyllum vortex (M'Coy). 



Sp. Char. Corallum simple, conic, slightly curved, enlarging at 

 the rate of 1 inch 8 lines in 3 inches from the apex ; outer wall 

 thin, faintly marked with subequal longitudinal lamellar striae 

 (five or six in the space of 3 lines at a diameter of 1 inch) and 

 small concentric wrinkles ; at a diameter of 1 inch the hori- 

 zontal section shows an outer area of about sixty thick, equal, 

 radiating lamellse barely reaching one-fourth of the diameter 

 towards the centre, connected by small irregular transverse 

 vesicular plates ; a few of the pairs have a very thin, short, 

 marginal lamella between each of the larger ones, and where 

 this occurs, the vesicular transverse plates become much more 

 numerous; inner area rather more than half the diameter, 

 forming a circular mass of confused vesicular tissue crossed 

 by a few arched radiating delicate lamellse : vertical section 

 having the narrow outer area on each side (corresponding to 

 the lamelliferous zone) of arched vesicular plates, forming large 

 unequal horizontal or slightly inclined cells, one or two ex- 

 tending across the width of the area ; wide inner area com- 

 posed of small oval cells arranged in much-curved transverse 

 rows, the convexity of the curve upwards. 



Wenlock limestone, Wenlock. 

 {Col. University of Cambridge.) 



Arachnophyllum typus (M'Coy). 



Syn. & Ref. Acervularia Baltica (Schw.), Lonsd. pars S. S. 1. 16. 

 f . 8 « (not of Schweigger). 



Sp, Char. Corallum forming thick, irregular, enveloping masses ; 

 upper surface undulated, covered with large shallow polygonal 

 stars, defined by very obtusely angular ridges ; the centres 

 averaging 7 or 8 lines apart, circular, depressed, rather more 

 than one-third the diameter of the star, radiated with about 

 thirty-eight strong granulose subalternate lamellse, half of 

 which reach the flattened centre, where they are irregularly 

 united and slightly twisted ; on the outer inclined area of each 

 star, each of the lamellae becomes much thinner and more 

 faintly marked, branching di- or tri-chotomously once or twice, 

 and often waving in a variable manner before reaching the 



l2 



