LIGIA. CRUSTACEA. 183 



FAMILY VI. ONISCIDES. 

 Gen. 21. LIGIA, Fab. Oniscus, Lin. 



Exterior antennae angular, approximated at the base, of six 

 joints, the terminal longest and jointed ; intermediate anten- 

 nas very small ; feet-jaws membranous, compressed, concave, 

 of ten joints ; body oval, of thirteen transverse segments ; two 

 bifid appendages at the extremity of the tail. 



The animals of this genus inhabit the shores of the sea, and crawl with facility. 

 L. oceamca, Lat. Exterior antennae one-half shorter than the 

 body ; styles of the tail nearly equal and as long as the tail ; co- 

 lour gray, with two large yellowish spots on the back. About an 

 inch long. Inhabits European coasts Desm. Crust. 317- 



Gen. 22. PHILOSCIA, Lat. Oniscus, Lin. 

 Exterior antennas naked at the base ; body oval, of seven trans- 

 verse segments ; tail of six segments, with four styliform ap- 

 pendages. 



P. muscorum, Lat. Upper part of the body cinereous, with scat- 

 tered points and lines of gray or yellow ; below whitish. Moist 

 places under stones and mosses in Europe. B. Desm. Crust. 319. 



Gen. 23. ONISCUS, Lin. 



Four antennas inserted under the anterior margin of the head ; 

 the two exterior only apparent and setaceous, and the inter- 

 mediate ones indistinct ; eyes sessile ; body oval, with crus- 

 taceous imbricated segments ; two projecting appendages at 

 the extremity of the tail. 



The insects of this genus are well known and very common. Their body is slight- 

 ly convex above, and furnished with seven pairs of short feet. Their motions are ge- 

 nerally slow, but they occasionally run with celerity. They appear to live on decayed 

 vegetables or fruits. The ova are hatched in an oval, thin, and flexible sac on the 

 under part of fhe body of the female, and the young, which have two feet and one 

 segment less in their body than the old, find shelter for some days in the respiratory 

 laminae of the parent. The Onisci were for a long time employed in medicine, as 

 being diuretic, absorbent, and aperient. 



O. asellus, Lin. Body slightly rugous above, particularly on the 

 head ; colour obscure gray, with the margin paler, and a longitu- 

 dinal series of yellowish points on each side of the body. 6 or 7 

 lines long. Common all over Europe. B Shaw, vi. pi. 135. 



Gen. 24. PORCELLIO, Lat. 



General characters of the preceding genus, but with the exter- 

 nal antennae inserted on a prominence under the anterior 

 margin of the head ; tail with the lateral styles slightly pro- 

 minent. 



P. scaber, Lat. (0. granulalus, Lam.) Head above and segments 

 of the body covered with numerous granulations ; fourth and fifth 

 joints of the antennae longitudinally striated; colour blackish ci- 

 nereous, yellowish, or gray. Inhabits Europe, under stones and 

 decayed wood Desm. Crust. 321. 



