CRUSTACEA. 
291 
B. The posterior pair of pleopoda formed into a ecale-like opercululn. 
1. The first four pairs of pereiopoda formed as ciliated swimming- 
appendages, without a claw. 6. ArcturidvE. 
2. Pereiopoda terminating in a claw, 6. InoxHEiDiE. 
II. A fin tail. Flat rami to the posterioi* pleopoda, or with ciliated swim- 
ming-appendages. 
A. With vertical side-rami. 7. Anthuridjb. 
B. Without side-rami. 
1. Generally seven pairs of appendage^s to the peieion; posterior pair 
of pleopoda 
a. With one ramus moveable. 8. SPHiEROMiD.®. 
b. With both rami moveable. 
aa. Sexes alike. 0. Cymathoidas. 
hb. Sexes very tinlike. 10. Bopyrida!. 
2. Five or six pairs of appendages to the pereion. 11. Anceid.®. 
After explaining his reasons for the above ftri'apgemeht, he 
gives a description of the genus Apseudes (Leach), and follows 
it with one of Apseudes talpa (Montagu). He then describes 
the genus Tanais (M. -Edwards), and follows it with an enume- 
ration of all the known species, and descriptions in Latin of all 
the new ones, which he arranges according to the annexed 
table. 
I. Posterior pair of pleopoda with two rami. 
A. First pair of hands of common form (subchelate F). 
1. Last joint of superior antenna shorter than first. 
a. Four joints to inner ramus of post, pleopoda. 1. oetstedii. 
b. Two joints to inner ramus of post, pleopoda. 2. brevicornis, sp. n, 
2. First and last joints of superior antenna of about same length. 
3. tenuimanu^, sp. il. 
B. First pair of hands chelate ; a large opening between the fingers. 
4. fordpatus, Sp. n. 
0. Hinder outer branch of the last pair of pleopoda two-jointed, and much 
shorter than the inner ramus. 
1. Hands having moveable fingers with the outer edge serrated or 
crenulated. 
a. Outer ramus of post, pleopoda hardly half as long as inner. 
6. graciliSf Kr. 
b. Outer ramus of post, pleopoda about half as long as inner. 
6. graciloideSj sp. n. 
2. Hands having moveable fingers, with the outer edge smooth. 
7. lo)7giremis, sp. n. 
D. Hinder outer branch of the last pair of pleopoda two-jointed, and little 
shorter than the inner ramus. 8. agidremis^ sp. n. 
E. Hinder outer branch of the last*pair of pleopoda one-jointed. 
9. breviremisy sp. n. 
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