398 SPH EROMIDA. 
The Sub-tribe SPH AAROMIDEA, 
ConsisTINe of the single 
Family SPH ZROMIDA, 
is distinguished by the comparatively small size of the 
species of which it is composed, which have the body 
short, broad, and very convex, often contractile into a 
ball, in both which respects they may be regarded as 
marine representatives of the terrestrial wood-lice. The 
foot-jaws are elongated, and in some species at least (e¢.9., 
Sph. serratum) they have the terminal joints not dilated at 
the inner apical angle, so as to become palpiform; but 
our numerous dissections prove that this character is not 
constant in those species in which these joints are consi- 
derably produced,—as in Spheroma Prideauxiana, Cymo- 
docea emarginata, &c. The head is large and transverse. 
The mandibles are robust and angulated at the extremity, 
the tips formed into several distinct teeth, below which 
is a strong molar tubercle. Externally, also, the mandibles 
are furnished with a palpiform three-jointed appendage. 
The first pair of maxille consist of two long slender 
lobes, the outer of which is most robust, and armed with 
a short strong spine at its tip, whilst the inner is ter- 
minated by long slender seta. The second pair of 
maxillz are very delicate and membranous, and termi- 
nated by three nearly equal-sized oval ciliated plates, 
forming the extremities of the three terminal joints. The 
upper antenne are fixed at the anterior margin of the 
head, which does not extend over them. All the antennz 
