ECHINUS. 151 
tubercle, and the rows formed by them are quite well marked. At 
the ambitus there are on the outer side of this primary tubercle 
two or three secondary tubercles, and on the inner side one or two; 
these disappear very regularly as either pole is approached ; there 
may be two rows of these secondary tubercles on each plate, or the 
second row may be replaced by one made up of a larger number of 
miliaries ; with these, at any rate, the rest of each plate is closely 
packed. 
On the ambulacral plates, of which there are about thirty in each 
row, a prominent primary tubercle is also to be noticed; this is 
placed just inside the rather wide poriferous zone ; between the two 
rows are a number of secondary and miliary tubercles, but they are 
not so closely packed as in the interambulacral area ; a few miliaries 
are scattered over the poriferous zone. The distribution of tubercles 
on the calycinal plates is not constant, but it frequently happens 
that the interradials have three or four largish tubercles on the edge 
nearest the periproct. 
Colour: the tips of the spines may be light or pinkish, but are 
more frequently purple; the test, when dry, may be dark grey- 
brown with pink bands, or have a more general pinkish or reddish 
hue. 
On the whole this is perhaps the species of Hchinus which presents 
less striking variations than any other found in our seas; even the 
differences due to age are slighter than is often the case. 
Diameter of 
Diam. — - ~ ~ Longest 
of test. Height. Peristome. Calye. area. Periproct. spine. 
34 17 13 35 4:5 
27 13 11°5 7 3d ae 
19 10 8 55 3 75 
16 9 8 + 2 
Distribution. The species extends northwards to Iceland and 
southwards into the Mediterranean ; North Sea. To 45 fms. 
a-c. Between Loch Reraig and Plocton, 8-24 John Murray, Esq. 
fms., 21/9/91. 
d-f. Loch Goil, 45 fms. (February). John Murray, Esq. 
g. Wilbrennan Sound, 10-20 fms. (March). John Murray, Esq. 
h, Whiting Bay, Arran. Rev. D. Lansborough. 
?. Kenmare River (July 1889). 
j-n. Lough Hoyle (July 1889). 
o. Ballywater. Belfast Nat. Hist. & 
Phil. Soe. 
p. Strangford Lough, 5 fms., 8/9/51. Belfast Nat. Hist. & 
Phil. Soe. 
g-s. Isle of Man. Prof, E. Forbes. 
t-v. Off Liverpool. 
w,x. Low water near Tenby (March 1889). 
y,z. Falmouth. W. P. Cocks, Esq. 
a’. Plymouth. 
‘, ec’. Plymouth. 
b',¢ 
d'—f, Weymouth (October). Edgar A, Smith, Esq. 
