REVISION OF PALEOZOIC STELLEROIDEA. 227 



''The adambulacral ossicles are massive and taper slightly to their 

 distal ends; they are closely attached and form a regular series of 

 marginal plates. 



''Arms very flexible. 



'^Dimensions: 



Length of longest arm 18 mm.+x 



Diameter of arm at the base 2.5 mm. 



Diameter of arm near the distal end 1 mm. 



Diameter of mouth 1.5 mm. 



Length of syngnath 1 mm. 



Width of ambulacral furrow at edge of disk 1.25 mm. 



"Distribution. — Wenlock Shale, Castell Dinas, Bran, near Llan- 

 gollen," Wales. Museum Practical Geology, London. 



4. 



24 25 



Figs. 24 and 25.— Protaster biforis. After Gregory. 24, ambulacraua and adambulacraua. 

 25, a, outline of the disk and arms; 6, a pair of syngnaths. 



PROTASTER GROOMI Sollas and Sollas. 



Protaster groomi Sollas and Sollas, Pliilos. Trans. Roy. Soc. London, ser. B 

 vol. 202, 1912, pp. 223, 224. 



Occurs in the IMiddle Ordovicic of Shropshire, England. 



PROTASTER (?) WmTEAVESIANUS Parks. 



Protaster xvhiteavesianus Parks, Trans. Canadian Inst., vol. 8, 1908, p. 3G8, 

 figs. 1-fi. 



This is a large form ^^'ith a disk 15 mm. across and witii rays 60 mm. 

 long. It is described in too much detail to quote here. The ambula- 

 cralia are distinctly alternate and boot-shaped. 



Formation and locality. — In the Lower Trenton (Kirkfleld), at 

 Kirkfield, Ontario, Canada. The cotypes (five) are in the University 

 of Toronto (No. 638 T.). 



PROTASTER (?) SALTERI (Salter). 



Ophiura salteri Salter and Soweuijy, Quart. Journ. Gool. Soe. London, vol. 1. 



1845, pp. 9, 20 (table) (nomen nudum). 

 Protaster salteri Wright, Mon. British foss. Echinod., Oolitic, vol. 2, pt. 1 (Pa]a>on- 



togr. Soc. for 1861), 1862, p. 33 (novun nudum). — Salter, Mem. Geol. Surv. 



Great Britain, vol. 3, 1866, p. 289, pi. 23, fig. 3 (is inclined to refer it to 



Txniaster). — Parks, Trans. Canadian Inst., vol. 8, 1908, pp. 364, 367. 



Formation ami locality. — The holotype is from the Ordovicic, near 

 Cerrig-y-Druidion on the Holyhead road, Wales. 



