c PORCUPINE ’ DEEP-SEA DEEDGING-EXPEDITIONS. 
723 
Lamarck, An. s. Vert. 1816; Cidaris jpapillata, Fleming, Brit. Animals, 1828; Cidaris 
hystrix, Blainville, Actinologie, 1834; Cidaris papillata, Forbes, Brit. Starfishes, 1841 ; 
Cidaris hystrix and Cidaris papillata, Agassiz, Catalogue raisonnee, 1846 ; Phyllacanthus 
hystrix , Brandt, Prod. 1835 ; Leiocidaris hystrix , Dujardin et Hupe, Echinoderms, 1862 ; 
JDoroddaris abyssicola, A. Agassiz, Bull. M. C. Z. 1869. 
The test in a mature full-sized example, from a depth of 200 fathoms off the south 
coast of Ireland (Plate LIX. fig. 1), is of a spheroidal form, gently depressed at the oral 
and apical poles. It measures 65 millims. in diameter from the centre of an ambulacral 
area to the centre of the opposite inter ambulacral area measured at the ambitus, and 50 
millims. in height from the edge of the mouth to the centre of the apical disk. The 
ambulacra are very narrow, 7 millims. in width between the outer edges of the pore- 
are®, and slightly sinuous ; and they present the same character and arrangement and 
are nearly of uniform width from the peristome to the ocular plates. The ambulacral 
plates form a narrow raised sinuous band along the centre of each ambulacral area, with 
a row of small tubercles along either side towards the pore-are®, and two rows of prin- 
cipal granules towards the centre of the band, with two or more imperfect rows of 
minute granules somewhat irregularly interspersed among them. The pore-are® are 
depressed, forming decided grooves. The pairs of pores are ranged in single series : 
there are from twelve to fourteen pairs opposite each of the large interambulacral plates 
of the ambitus. The pores of a pair are close together but not contiguous. It can 
scarcely be said that they are connected together by a groove, but rather that a slight 
ridge runs out between the pairs of pores from the marginal tubercles of the ambulacral 
plates, and abuts against the edge of the adjoining interambulacral plate. 
The interambulacral spaces are very wide, about 35 millims. in their widest diameter. 
They consist of two rows of large plates, in full-sized examples seven in each row, dimi- 
nishing to either end ; and the smallest plate at either end of the area belongs to the 
right or left row alternately. On each plate there is a large, smooth areola, greatly 
depressed, and occupying nearly the whole area of the plate. The areolae round the 
ambitus are 12 millims. in diameter, round or slightly elliptical ; they are bounded by 
an abruptly elevated border, and show no tendency to coalesce, except occasionally in 
the case of some of the smaller plates round the peristome. A very definite row of from 
twenty to thirty small tubercles with distinct smooth articulating surfaces border each 
areola ; and the spaces between the areolae are closely crowded with miliary granules, 
which decrease in size towards the line of junction between the two rows of plates. A 
boss with a smooth uncrenulated edge rises in the centre of the areola, and is surmounted 
by a smooth tubercle of moderate size with a large deep central perforation. The 
apical opening in the corona is large and nearly round. The ovarial plates are large, 
irregularly rectangular or shield-shaped, somewhat narrower towards the edge of the 
disk, where they abut against the inner halves of two terminal interambulacral plates of 
an area, and expanding inwards where they come in contact with the small plates of the 
periproct. One ovarial plate is much larger than the others, and shows the usual 
