No. 402.] MWORTH-AMERICAN INVERTEBRATES. 515 
Key to Species. 
A. Posterior margin of carapace d aues or nearly so. Cardiac region 
faintly indicated . : . C. concava Stimpson, G 
A’. Posterior margin of carapace sinuous. Cardiac region protuberant 
C. occidentalis Dana, PD 
Genus Heterocrypta Stimpson . . . . H. granulata (Gibbes), SGM 
TRIBE OXYSTOMATA OR LEUCOSOIDEA. 
Carapace with the antero-lateral margins arcuate or orbiculate ; some- 
times subglobose or more or less oblong, with subparallel margins. Epi- 
stome much reduced. Buccal frame more or less triangular, produced and 
narrowed forward, with the margins anteriorly convergent. Six to nine 
Fic. 11. — Lambrus pourtalesii. 
pairs of branchiz. Efferent channels opening at the middle of the endo- 
stome, which is produced forwards. The afferent channels open either 
behind the pterygostomian regions and in front of the chelipeds, or at the 
antero-lateral angles of the palate. First antenna folded longitudinally or 
obliquely. The genital organs of the male are exserted, either from the 
bases of the fifth pair of legs, or from the surface of the sternal plastron. 
KEY TO THE FAMILIES OF THE TRIBE OXYSTOMATA. 
4. Legs normal in size and position. 
B. goes not closing the buccal cavern; their palp always ex- 
pos . CALAPPIDJE Milne-Edwards, de Haan, White 
B. Maxillipeds. desig the buccal cavern; the palp hidden. 
C. Afferent branchial openings in front of the bases of the 
chelipeds . . Matutip# M'Leay 
C'. Afferent branchial PRENS on either side of the endostome 
Leucosup Leach 
