84 J. R KiNAHAN on the Britannic Species of 



to the somite ; the ischium dilated into a cutting edge, behind which the suc- 

 ceeding articulations are folded down. 



The fifth pair (first maxillae, Fig. X. 5) is three-jointed; thecoxas soldered 

 as before ; the ischium armed with teeth on its inner edge, and bearing a se- 

 condary appendage. That this plate is respiratory is shown by its position and 

 structure, as distinct chains of respiratory tubes may be seen traversing its 

 structure, and terminating at the base of the articulated hairs with which its 

 borders are fringed. In structure it is but slightly simpler than the respiratory 

 lobes found attached to the abdominal somites in many of the subterranean 

 Crustacea (ex. gr. Trypaea porcellana). 



The seventh pair (third maxillae. Fig. X. 7) is two-jointed ; the coxae 

 membranous, except a linear longitudinal ridge, which is calcified, dilated ex- 

 ternally into a respiratory plate (z), from the upper margin of which the acces- 

 sory appendage (x) springs. The basis completes the limb ; its inner edge is 

 straight, sparingly denticulate, and ciliated with thick-set long hairs, and also 

 bearing a raised ridge set with hairs •, its outer margin is curved. By some 

 this limb is looked on as three-jointed, the coxa being represented by a small 

 squared membranous plate, internal to the calcified column, and the ischium 

 bearing what is here called the respiratory plate and its appendage ; but I can- 

 not agree to this view ; and as to the objection, that in the other limbs the 

 ischium always bears the most important cutting edge, an examination of the 

 external maxilliped shows that the basis also may bear a set of teeth, even 

 when the ischium is present. 



The eighth pair (internal maxillipeds) (Fig. X. 8) is seven-jointed, the 

 basis squared, the ischium (i) toothed on its inner edge, which shows a double 

 ridge, and is fringed with hairs ; the accessory appendage (x) is two-jointed, 

 arising from the coxas, but also articulated to the basis. 



The external maxillipeds (ninth pair of limbs) are seven-jointed, and bear 

 a secondary appendage, which arises from the outer superior angle of the coxa;, 

 and is articulated by a lateral process to the basis. The appendage is four- 

 jointed; the basal joint short and imperfect, the second long, the third short 

 and slender, and the fourth a curved, flattened, multiarticulate, hairy filament. 

 A lateral process of the coxse bears a set of branchial palps and plates articu- 

 lated to it. Query — Is the office of the appendage gustatory ? The basis and 



