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The Sub-tribe SPH^EEOMIDEA, 

 CONSISTING of the single 



Family SPH^ROMID^, 



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.g., 

 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 Sphceroma 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 maxillae 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 setae. The second pair of 

 maxillae 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 antennae are fixed at the anterior margin of the 

 head, which does not extend over them. All the antennae 



