148 ECHINOIDEA. 
Echinus flemingii, A. Ag. Bull. Mus. C. Z. i. (1862) p. 262. 
Echinus depressus, G. O. Sars, Vid.-Selsk. Forh. 1871 (1872), p. 23. 
Kcbinus elegans, Bell, Journ. Linn, Soe. 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. Pedicellariz pretty 
numerous, some with the three valves very thick at their base, 
though not so fleshy as in L. 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 
A 
Diam. of Height of — 
test. test. Peristome. _— Calye. area. Posen 
15 6-5 55 Ms) 2°5 
15 8 5 a7 27 
14 a 52 na we 
12 7 5) 4:8 2 
10 5°25 4-3 4 2 
10 4-75 3°25 37) 2 
* 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. 
