British Species allied thereto. 475 



noticeable reduction of the spines in the specimen from 

 Plymouth (fig. 6) that one might be inclined to suppose that 

 spinulation becomes less coarse and more scanty in more 

 southern latitudes, were it not that specimens equally poor in 

 spines can be taken off the west coast of Scotland • a speci- 

 men from Kenmare River is more like that figured from 

 Plymouth than like that shown in fig. 3, which came from 

 the south-west coast of Ireland . Forms with as blunt spines 

 as those from the Seaham specimen (fig. 4) may be taken 

 from the Shetland waters, and such spines may be loosely or 

 closely packed. The specimen (fig. 5) from Cullercoats 

 could be duplicated from St. Andrews. Enough perhaps has 

 been said on the subject of spinulation. 



The general appearance of a starfish is, of course, largely 

 affected by the relations of the radius of the disk (r) to the 

 length of the arm (R). Specimens from Kilbrennan Sound 

 show R = 6'5 r, R = 6 r, R=4*5 r ) from Cullercoats we get 

 R = 5 r or R = 4 r\ two specimens from Plymouth give R = 

 5*5 r and R = 4 r; so here again there is variation without 

 any apparent relation to locality. 



Yet, again, the breadth of the arms at the base affects the 

 habit or general contour of the spines, and this too is liable 

 to considerable variation. 



Forbes laid particular stress on the form of the ambulacra ; 

 but it will be found that the pyriform lanceolate shape is often 

 associated with a sharp spinulation, and not with the blunter 

 form which is characteristic of "A. violacea." 



Some noticeable variations in length and breadth may be 

 seen in the table which follows : — 



Greatest breadth of arms 



I am brought therefore to the conclusion that Asterias 

 ruhens and A. violacea are not to be distinguished, and I 

 offer the following diagnosis : — 



