378 CRUSTACEA 



Family 10. JANIRIDAE. 



Body flattened and similar to the Asellidae, with the side of the head 

 usually expanded under the eye; first pair of abdominal appendages in 

 the female form a single large opercular plate, and 

 in the male together with the second pair form 

 a compound operculum: 20 American species; 

 marine. 



1. J^RA Leach. First pair of antennae very 

 small; uropods very small: 2 American species. 



J. marina (Fabricius) (Fig. 603). Body 

 oval, 5 mm. long, 2 mm. wide, and very variable 

 in color, usually being mottled gray; legs ambu- 

 latory and triunguiculate : coast of New England ; 



Fig. 603— Jorra marina Europe; common between tide lines under stones 

 (Harger). ^ ' 



and seaweeds. 

 2. Janira Leach. First pair of antennae and uropods well devel- 

 oped ; side of head not expanded, or but slightly so : 5 American species. 



J. alta (Stimpson) (Fig. 604). Length 7 mm.; 

 width 2 mm.; legs biunguiculate : Atlantic coast from 

 Nova Scotia to Virginia, from low-water mark to 500 

 fathoms. 



Family 11. ONISCIDAE. 



The sow bugs. Terrestrial isopods with an 



elliptical body, which is more or less flattened and 



cannot be rolled into a ball (except Cylisticus con- 



vexus) ; first antennae minute; second antennae long; Fig. 604 — Janira 



. , -, ■ , n «^^» (Harger). 



thorax with 7 and abdomen with 6 free segments; 



legs ambulatory; 5 pairs of pleopods are respiratory plates, the second 



pair in the male terminating in a pair of long slender stylets; uropods 



long and terminal : common under logs, etc., and in other dark, damp 



places on the land; 200 species, 30 American. 



Key to the genera of Oniscidae here described : 



«! Antennae ending with 3 short segments forming the flagellum. 



&i Abdomen not abruptly narrower than thorax 1. Oniscub 



62 Abdomen abruptly narrower than thorax 2. Philoscia 



a-a Antennae ending with a flagellum of 2 short segments. 

 hi Abdomen not abruptly narrower than thorax. 



Ci Body convex, can be rolled into a ball 3. Cylisticus 



Cj Body flattened, cannot be rolled into a ball 4. Pokcellio 



6a Abdomen abruptly narrower than the thorax 5. Metoponorthus 



1. Oniscus L. Body broad, flattened, with a granulated or tuber- 

 culated surface; antennae ending with 3 short segments; side of head 

 extended beneath the eyes: 1 species. 



