156 RITTER. [Vou. XII. 
sometimes reach a length of 46 cm., while I have never seen a 
colony of G. dura more than 10 cm. in length, 
The branchial and atrial apertures of cocc¢nea are conspicuous 
and are irregularly four-lobed; in dura they are not conspic- 
uous, and in preserved specimens show no trace of lobes. In G. 
coccinea the “‘meshes”’ of the branchial sac, z.e. the areas of the 
sac between the internal longitudinal vessels, contain eight 
stigmata. In G.dura the number is not the same in all the 
meshes, but at the most is less than eight; at the least it is 
three. But probably the best distinction between the two 
species is in the character of the stomach. In G. coccznea this 
organ, as described by Herdman, is globular in form, and con- 
cerning its folds he says: ‘There are usually six well-marked 
folds upon the right side of the stomach. A transverse section 
shows in addition a single large fold, which projects far into 
the centre, nearly dividing it into two cavities.” Reference to 
my Figs. 4 and 6, Pl. XII, shows at once that the stomach of 
G. dura is quite different from this. In the first place it is 
not globular. It is rather schizaster-shaped, if I may be per- 
mitted to suppose that the form of this echinoid is any more 
familiar than that of the stomach which I am comparing with 
it; but I can think of no other object which it so closely 
resembles in form as it does some species of this genus. In 
the G.dura stomach there is no one fold that exceeds the 
others in the extent to which it projects into the chamber. 
Another distinction between the two species, that would 
appear to be constant, consists in the presence in G. coccinea 
of a vessel which, ‘enclosed in a prolongation of the mantle, 
leaves the posterior end of each Ascidiozooid and runs for a 
longer or shorter distance through the test before ending in a 
dilated bulb.”’ No such vessel occurs in G. dura. 
Although it is evident from Gottschaldt’s description of 
G. borealis that this species and G. dura are closely related, it 
is unfortunately impossible to make as exact a comparison 
between them as is desirable, owing to the incompleteness of 
the author’s description at one or two critical points. In the 
form of the colony they appear to agree more closely than 
either agrees with G. coccinea, for the figure representing a 
a 
