PORCELL10. 473 



ISOPODA. ONISOID^E. 



NORM A LI A. 



Genus PORCELLIO. (Latreille.) 



Generic character. Ovate, sub-depressed. Cephalon with 

 large lateral lobes. Outer antennae seven-jointed. Coxse of 

 the second and sixth segments of pleon obsolete. Terminal 

 uropoda with the basal portion triangular, flattened. Apical 

 portion compressed, trigonate, exserted. Inner appendage small, 

 curved, and trigonate, concealed by the last segment of the 

 pleon, which is more or less concave on its upper surface. 



THE animals of this genus differ from those of 

 Armadillo (which they resemble in having only seven- 

 jointed outer antennas), in the form of the second 

 joint of those organs, which is not furnished with 

 a rounded lobe on the outside at its extremity a 

 peculiarity dependent on the different arrangement of 

 the front part of the head, and the consequent manner 

 in which these organs are disposed when at rest, the 

 remarkable groove at the sides of the front of the head 

 being here wanting. The late Professor Kinahan thus 

 described the structure of the front of the head in 

 Porcellio : 



"External angles of the third antennary segment of 

 the head more developed than in Oniscus, the superior 

 margin raised into a lobe, which projects above the 

 frontal line of the cephalic segment, and gives the head 

 a trilobed appearance. This lobe, though sometimes 

 badly marked (Porcellio pruinosus, Br. P.frontalis Lereb., 

 not Edw., for example), is present in all the species I 

 have had an opportunity of examining." 



