304 THE AMERICAN NATURALIST. [VOL. XXXIV. 
Genus Porcellio Latreille. 
a. Surface of body smooth. 
à. Frontal median lobe of head rounded, a little produced. Articles 
of the flagellum of the external antenna equal in length. Last 
segment of the abdomen with its extremity widely rounded. 
Porcellio formosus Stuxberg, California 
&. Frontal median lobe of head more acute, minute. First article of 
the flagellum of external antenne equal in length to the other, or 
a little longer. Last segment of the abdomen with its extremity 
acute. . . . . . Porcellio levis Latreille, North America 
Fre. 15. — Alloniscus perconvexus. Fic. 16. — Actoni llipti 
a’. Surface of body roughly granulate or tuberculate. 
6. Inner mala of the mandibles with four to five pencils of hairs. 
Body with spots. 
c. Third joint of the peduncle of the second pair of antenne fur- 
nished with a small apical tooth. Frontal lateral lobes of 
moderate size. Color varying from gray to black, with three 
longitudinal lines of white spots. Flagellum with joints sub- 
equal, or first shorter than second. 
Porcellio rathkei Brandt, North America 
c. Second joint of the peduncle of the second pair of antennz 
furnished with a large apical tooth. Frontal lateral lobes 
large. Color yellow; body spotted with black, spots arranged 
in longitudinal lines. Flagellum with first joint a little longer 
than second joint. Porcellio spinicornis Say, North America 
&. Inner mala of the right mandible with four to five pencils of hairs, 
of left mandible with seven to eight pencils. Body without 
spots. Frontal lateral lobes of head large, oblique. 
Porcellio scaber Latreille, North America 
