148 ECHINOIDEA. 



Echinus flemingii, A. Ag. Bull. Mus. C. Z. i. (1862) p. 202. 

 Echinus depressus, G. 0. Sars, Tul-Selsk. Fork. 1871 (1872), p. 23. 

 Echinus elegans, Bell, Journ. Linn. Soc. xvii. (1884) p. 102 *. 



All the specimens in the Collection known to come from the 

 British area belong to the small form of this species, which it will 

 be sufficient to describe in detail. 



The test is conspicuous by a reddish, much more rarely greenish, 

 patch in the middle of each ambulacral and interambulacral area. 

 In the latter the patch may be wide and extend to the ambitus ; in 

 the former it may be wedge-shaped. In many dried tests the latter 

 and in some the former also may completely fade away. The test 

 is more or less depressed or conical, flat beneath, with rather large 

 peristome, calycinal area and periproct, all of which are or may be 

 juvenile characters, but are in this case found in a form which 

 has been shown to have matured gonads. 



Primary spines white, sometimes red at base, often rather long 

 and delicate, nearly the diameter of the test, not very numerous, 

 sometimes a good deal shorter and then rather stouter and yellower 

 or greenish in hue. A moderate number of well-developed smaller 

 spines, most numerous below the ambitus. Pedicellariae pretty 

 numerous, some with the three valves very thick at their base, 

 though not so fleshy as in E. microstoma. 



Ten or eleven plates in each row of the interambulacra, with 

 a single, central, large primary tubercle ; below the ambitus the 

 secondaries are pretty numerous, above it they are much more 

 sparse. The interambulacra are wide owing to the width of the 

 poriferous zones ; these are the most noticeable when there is an 

 intermediate reddish wedge-shaped patch above the ambitus, 

 above which the large primaries are not developed, and only a few 

 scattered secondaries are to be found. The size and number of the 

 tubercles is, however, subject to some considerable variation. 



The calycinal area is often remarkably prominent, either because 

 of the coloration of the area or the raising up of its constituent 

 plates ; the radials are all shut out from the periproct, the inter- 

 radials are rather large, and there are three or four granules along 

 the inner edge ; the number of granules on the interradials is 

 inconstant. The peristome is large and nearly circular, its mem- 

 brane is remarkable for the large quantity, small amount, or absence 

 of calcareous plates. 



Diameter of 



* Echinus rarispina of Thomson (Phil. Trans, clxiv. p. 744) and of Hoyle 

 (Proc. R. Phys. Soc. Ed. x. p. 417) are references to a MSS. species of Sars. 



