Sladen — Echinodermata from the 8. W, Coast of Ireland. 699 
closely than that of the figure given by Mr. "W. E, Hoyle^ of 0. sig- 
nata; and the uppermost arm-spine is not so long as described by 
Verrill, it being scarcely longer than the middle one. 
4. Ophiopholis lellis (Linck), Lyman. 
Depth 50 and 54 fathoms. 
5. Ophiothrix fragilis (0. F. Miiller), Miiller & Troschel). 
Depth 5 and 50 fathoms. 
6. Ophiohursa hystricis, Lyman. (?) 
Locality. — About 56 miles off Dursey Head. Depth 345 
fathoms. Fragments of rays only, in bad state 
of preservation. 
lY.-ECHIJS'OIDEA. 
L Borocidaris papillata (Leske), A. Agassiz. 
Locality. — About 56 miles off Dursey Head. Depth 345 
fathoms. 
2. Porocidaris gracilis, n. sp. (Plate XXIX., figs. 1-5.) 
Form circular, sub-globular, depressed, the height when measured 
from the summit of the convex apical system is nearly three-tourths 
of the breadth, or in the proportion of 72 per cent., the greatest 
diameter being 18 mm., and the height 13 mm. The test is depressed 
on the abactinal surface, moderately inflated at the ambitus, and 
gradually contracted below that line. 
Ambulacra straight and very narrow, the breadth being slightly 
less than one -fourth the breadth of the interambulacral area at the 
widest part. Poriferous zones only slightly sunken ; pores very 
small, in simple pairs, conjugate ; the pairs placed obliquely, the 
inner pores being the lowest ; and there are five pairs of pores opposite 
one of the largest interambulacral plates. The interporiferous area 
has a breadth of exactly one-half the width of the whole ambulacral 
area, and is'ffurnished with two rows of small mammillated miliary 
tubercles, that is to say, one tubercle to each plate, which occupies 
the whole space between the poriferous zone and the median suture, 
and no granules are present. 
1 " Proc. Roy. Soc. Edin.," vol. xii., pi. vii., fig. 6. 
