No. 400.1] MORTH-AMERICAN INVERTEBRATES. 297 
a’. Lateral margins of head not entire. 
à. Lateral margins of the head with a deep cleft on either side. 
Mancasellus macrourus Garman, Ky., Tenn. 
2’, Lateral margins of the head with a large rounded sinus on each side 
in the middle. 
c. External antennz as long or longer than the body. 
Mancasellus lineatus (Say), South Carolina 
c. External antenna half as long as the body. 
Mancasellus tenax Harger, Lake Superior 
Genus Asellus Geoffroy. 
a. Caudal stylets, or uropoda longer than terminal abdominal segment. 
Post-lateral margins of head without spines. 
6. Caudal stylets broad and flattened. Propodus of first pair of legs 
much enlarged and subglobular, with a prominent acute tooth 
about, or a little above, the middle, and a lobe bearing one or two 
acute teeth near the base on its palmar margin. 
Asellus communis Say, Conn., Penn., Ind., Il., Mich., Miss. 
&. Caudal stylets extremely narrow and cylindrical. Prapodüs of first 
pair of legs narrow, elongate, without prominent acute teeth on 
its pen margin. 
Asellus attenuatus Richardson, Virginia 
a’. Caudal stylets shorter than terminal abdominal segment. Post-lateral 
margins of head produced into prominent lobes bearing spines. 
à. Post-lateral lobes bearing each several stout spines. Lateral margins 
of all the thoracic segments except the first with no emargination. 
Flagellum of first pair of antenne consists of eleven to thirteen 
joints. Caudal stylets broad and flat, half as long as terminal 
abdominal segment . . . Asellus brevicauda Forbes, Illinois 
&. Post-lateral lobes bearing each a single spine. Lateral margins of 
all the thoracic segments except the first distinctly emarginate. 
Flagellum of first pair of antennze consists of nine joints. Caudal 
stylets broad and flat, but narrower than in 4. brevicauda, and 
three-fifths as long as terminal abdominal segment 
Asellus intermedius Forbes, Illinois 
Asellus tomalensis Harford, California 
The description of this form is so meagre and insufficient that it is 
impossible to place it in the key with the other species of Asellus. 
Genus Czcidotea Packard. 
4. Caudal stylets nearly half as long as body; basal joint or peduncle 
nearly twice as long as inner ramus; outer ramus from one-third to 
one-half as long as inner branch. First pair of antenne short, reach- 
ing but little beyond the second joint of the second pair of antenne. 
Cecidotea stygia Packard, Ind., Ill., Ky. 
a’. Caudal stylets no longer than terminal abdominal segment ; basal joint 
or peduncle shorter than innér ramus; outer ramus most as long as 
