No. 400.] JVORTH-AMERICAN INVERTEBRATES. 303 
the first joint generally longer than the second, often subequal, 
or even alittle shorter. Last abdominal segment generally not 
reaching beyond the epimera of the preceding segment. Ex- 
ternal branches of the uropoda longer in the male than in the 
female. External opercular branch of the first and second pairs 
of abdominal appendages, and, in some of the species, of all 
the pairs, furnished with trachee . . .  Porcellio Latreille 
Flagellum of external antennz triarticulate. External opercular ramus 
of the abdominal appendages containing no special respiratory organ. 
b. Front of head produced at the middle and at the sides in tubercles ; 
lateral tubercles hornike . Alloniscus Dana 
&. Front and sides of head not brodiond 4 in EN With or with- 
out lateral lobes. 
c. Abdomen abruptly narrower than the thorax. Epimera of 
thoracic segments small. Epimera of abdominal segments 
. very small, but manifest. External branches of the uropoda 
styliform . . Philoscia maye 
cœ. Abdomen not svipür- narrower r hes horas. Epimera of 
thoracic segments large. Epimera of abdominal d 
arge. External branches of the uropoda conica 
d. Surface of body granulated or tuberculate. pea of all 
the thoracic segments with the posterior angle acute. 
Basal article of the uropoda oblong, with the outer side 
obliquely carinated. . Oniscus Linnzus 
d'. Surface of body setigerous, acsi: Tandika. Epimera 
of the first three thoracic segments with the posterior 
angles roundly obtuse, of the fourth segment straight, 
d of the other segments acute. Basal article of the 
uropoda short and broad, with the outer side sulcate. 
Lyprobius Budde-Lund 
, 
a. 
Genus Metoponorthus Budde-Lun 
a. Inner-mala of the right nina with four to five, of the left mandible 
with six pencils of hairs. Second and third joints of the peduncle 
of the second pair of antenna furnished with a small apical tooth ; 
first joint of flagellum much longer than second joint. No middle 
frontal lobe. Color brown, or reddish-brown 
Metoponorthus pruinosus Brandt, North America 
a’. Inner mala of the right mandible with four, of left mandible with five 
pencils of hairs. Second and third joints of the peduncle of the 
second pair of antennae without small apical tooth; first joint of 
flagellum shorter than second. Middle frontal lobe small, widely 
rounded. Color varying from gray to black, with three longitudinal 
lines of white spots . Metoponorthus virgatus Budde-Lund, Florida 
Genus Cylisticus Schnitzler. 
Cylisticus convexus De Geer, North America 
