exotic Sesstle-eyed Crustaceans. 187 
dered together. The second division is nearly three times as 
long as the first, and for two thirds of its length is much in- 
flated; it then becomes slightly constricted and considerably 
depressed. Of the caudal appendages the outer plate is much 
smaller than the inner both in length and breadth, and is oval 
in shape. ‘The inner plate follows much the same curve along 
its free border ; but, where it closely adjoins the tail-segment 
to which it is united, it has aslight concavity fitting the corre- 
sponding convexity of the tail-piece. On the underside of 
the animal a broad fold of this last tail-segment stretches the 
whole length of each side of it; beneath the narrower part 
of the segment the edges of these folds meet. 
There is a species of Spheroma (Spheroma Juriniz) described 
by Milne-Edwards from the Egyptian crustaceans of Savigny 
and Audouin, of which he says :—“ This species appears to be 
very near to Spheroma serratum, butis distinguished from it 
by the form of the last segment of the abdomen, which is pro- 
longed backwards into an obtuse pomt. The external plate 
of the caudal appendages has its edge smooth. The length 
is about two lines.”” This, as far as it goes, might fairly suit 
the present species; but as nothing is said of the great dif- 
ference in size between the plates of the caudal appendages, 
which are in consequence very unlike those of Spheroma ser- 
ratum, there can be little doubt that the present is a distinct 
species, for which I propose the name of Sphwroma algoense. 
It is scarcely of importance to mention that both this and 
Seba Saunders are light yellow in colour, since the colour 
may have faded or changed since the animals’ deaths. It 
may be remarked, too, that some of our English species of 
Spheroma are exceedingly variable in colour. 
IV. Before closing this paper, I may observe that along 
with the new species some very small specimens have pre- 
sented themselves of Arcturus lineatus, described and figured 
in the ‘Annals’ for August 1873, above referred to. The 
point demanding notice in reference to these young specimens 
is that the fourth segment of the thorax is not elongated as 
in adult life—a point the more interesting, because upon this 
character Milne-Edwards grounds a division of the genus Arc- 
turus into two sections :—one containing the large Arcturus 
Baffint from Baffin’s Bay, which has the segment in question 
not elongate ; the other containing the British Arcturus longi- 
cornis, which has this one segment as long as all the other 
body-segments put together. Of these sections Goodsir made 
a genus Arcturus and a genus Leachia—a division obviously 
now inconvenient, since according to it our Arcturus Uneatus 
