12 Prof. J. C. Schiodte on the Structure of 



body-limbs are not hooked, but long prehensile organs, arti- 

 culating with the body in such a manner that they can reach far 

 forward in order to catch objects, and then, folded together, 

 keep that which has been caught closely under the mandibles ; 

 the second pair of legs, which have the same shape but in a 

 smaller size, are to be considered merely auxiliary organs. 



9. These three types may consequently be surveyed accord- 

 ing to the subjoined scheme : — 



Instrumenta cibaria mordentia, libera, serie obliqua utrinque 

 disposita. Hypostoma breve. Orificium oris amplum. 

 Mandibulse malis binis instructee, exteriore fixa. 



A. Mala exterior mandibularum mola instructa striata, 

 mucronulata spinosave. 



a. Os manducatorium. 



Mala exterior mandibularum ramosa, digitate spi- 



nosa, prensoria. 

 Maxillse priores malis binis, exteriore subrecta, 

 apice spinulosa. 



Oniscij AselU, Idothece, Sphceromata. 



B. Mandibulse mola carentes. 

 h. Os sectorium. 



Mala exterior mandibularum depressa, quadrata, 



margine interiore acutissimo, valide dentato. 

 Maxillse priores malis binis, exteriore incurva, 

 multispinosa. 

 Girolance. 

 c. Os morsorium. 



Mala exterior mandibularum crassa, fornicata ; 



margine crasso, obtuso, edentulo. 

 Maxillae priores mala unica, apice spinulosa. 

 Serolides. 



10. Thus prepared, we may with greater confidence enter 

 upon an examination of the structure of the oral sucking-ap- 

 paratus in Cymothoge. As examples we may take two often- 

 described species, jEga psoi^a^ L., and Cymothoa oestrum, auct., 

 which represent the two types round which all the other Cy- 

 mothose gather themselves with regard to the construction of 

 their sucking- apparatus. For the sake of comparison I also 

 take into account the Ayiilocra Leachii, Kroyer, a new spe- 

 cies from the West Indies, which approaches very near to A. 

 laticaudttj M.-E. (Hist. Nat. des Crust, iii. 259. 6), besides a 

 small species nearly related to Cymothoa sens, str., which was 

 collected by Professor Kroyer, in Feb. 1840, on a fish caught 



