CIDAEIS. 141 



interambulacral plates in each row ; the areole round each primary 

 tubercle is wide and deep ; the tubercle is perforated, but its base 

 is not crenulated ; the remaining portion of each plate is closely 

 covered with miliaries ; as a rule the circlet of tubercles is complete, 

 but it sometimes happens that only one row of tubercles divides one 

 areola from one of its neighbours. 



In the calycinal area the periproct has a pentagonal form, and 

 the angles of the pentagon are produced along the lines of the radii, 

 a triangular plate separating each of the radials and touching the 

 interradial by its pointed apex ; the interradials are kidney-shaped in 

 form, with the long axis at right angles to the line of the ray ; the 

 radials vary a good deal in contour, but are always wider along their 

 inner than their outer edge, and are generally notched at the sides. 



Peristome rather large, about the same size as the calycinal area. 



Distribution. Very wide. " We dredged it in from 100 to 400 

 fathoms wherever there was a gravelly or sandy or in any way 

 a hard bottom, in one continuous belt from the Faeroe Islands to 

 Gibraltar .... In some localities the number of individuals was 

 quite surprising. In the Shetland Sea, and at some stations off the 

 South and West of Ireland, the dredge-bag was almost choked with 

 them" (Wyv. Thomson, Phil. Trans. 1874, p. 725). Prof. A. 

 Agassiz has himself (Chall. Rep. Ech. p. 38) thrown doubt on his 

 correct identification of Pacific forms as belonging to this species. 

 0-874 fms. 



a. Off coast of Kerry, 100-200 fms. Royal Irish Academy. 



b. Off S.W. coast of Ireland, 250 fms. * Flying Fox ' Exp. 

 c-n. Off S.W. coast of Ireland, 150-315 fms. < Flying Fox ' Exp. 



o. Off S.W. coast of Ireland (young). ' Flying Fox ' Exp. 



p. Off Wexford, 30-40 fms. ' Porcupine ' Exp. 



q, r. 49^ & 50° N., 11° W., 200-400 fms. G. C. Bourne, Esq. 



s, t. 40 miles off Achill Head, 144 & 220 fms. R. Dublin Soc. 



u. 45 miles off Blackrock, 500 fms., 12/5/91. R. Dublin Soc. 



v. 45 miles off Blackrock, 250 fms,, 12,5 9] . R. Dublin Soc. 



2. Cidaris pnrpurata. 



Porocidaris pnrpurata, Wyv. Thorns. Phil. Trans, clxiv. (1874) p. 728, 



pi. lix. tigs. 14, 15, pi. lxi. 

 Cidaris purpurata, Duncan, J. Linn. Soc. xxiii. (1889) p. 32. 



Some of the primary spines are swollen in their basal half, which 

 is coloured purple. A few of the spines are a little longer * than 

 the diameter of the test ; some are almost smooth, others a good 

 deal serrated ; those around the mouth are flattened and spatulate. 



* Twice and more as long, testeWjv. Thomson. 



