ORDER ISOPODA. 215 



hoolis. They have at then- base an elongated vesicular body. 

 These laemodipods form the subgenus of C YAM US (proper) » 

 Lat. Larunda, Leach. {Oniscus ceil, Lin.) 



THE FIFTH ORDER OF CRUSTACEA. 



ISOPODA, 



Polygonata, Fab., the genus Monvculus excepted, 



Approach the leemodipods by the want of palpi to the mandi- 

 bles, but they are remote from them in many respects. The 

 two anterior feet are not annexed to the head, but depend, as 

 well as the following, on a peculiar segment ; they are always 

 fourteen in number, unguiculated, and without vesicular ap- 

 pendage at the base. The under part of the tail is furnished 

 with very apparent appendages, in the form of leaflets or vesi- 

 cular pouches, and the first or the exterior two usually cover 

 totally, or in a great part, the others. The body is generally 

 flatted, or more wide than thick. The mouth is composed of 

 the same pieces as in the preceding Crustacea ; but here the 

 parts which correspond to the two upper jaw-feet of the deca- 

 pods present still more than in these last the appearance of a 

 lower lip, terminated by two palpi. Two of the antennoe, the 

 middle, are almost obliterated in the last Crustacea of this 

 order, which are all terrestrial, and differ from the last in their 

 respiratory organs. The male sexual organs are most fre- 

 quently announced by the presence of linear or filiform ap- 

 pendages, and sometimes of hooks, placed at the internal 

 origin of the first subcaudal laminse. The females carry their 

 eggs under the breast, &c. 



