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 ; tbe test, when dry, may be dark grey- 

 brown with piuk bands, or have a more general pinkish or reddish 

 hue. 



On the whole this is perhaps the species of Echinus 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. 



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. 



y. Kilbrennan Sound, 10-20 fms. (March). John Murray, Esq. 

 h. Whiting Bay, Arran. Kev. D. Lansborough. 



i. Kenmare River (July 1889). 

 j-n. Lough Hoyle (July 1889). 



o. Ballywater. Belfast Nat. Hist. & 



Phil. Soc. 

 p. Strangford Lough, 5 fms., 8 9/51. Belfast Nat. Hist. & 



Phil. Soc. 

 q-s. Isle of Mau. Prof. E. Forbes. 



t-v. Off Liverpool. 



w,x. Low water near Tenby (March 1889). 



y, s. Falmouth. W. P. Cocks, Esq. 



a'. Plymouth. 

 b ', c . Plymouth. 

 d'-f. Weymouth (October). Edgar A. Smith, Esq. 



