54 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



Paqueta, Bay of Bahia, Brazil; 3-4 fathoms; 187G-1877; R. 

 Rathbun; 1 female ovig. (16267). 



Rio de Janeiro? ; U. S. Exploring Expedition; 2 males (1 is holo- 

 type) (2332). 



Jurujuba Bay, Rio de Janeiro; 1876-1877; R. Rathbun; 1 male 

 (16268). 



Other records. Sombrero Key, Florida (A. M. Edw.) ; Port of 

 Silam, Yucatan (Ives). 



Subfamily RHIZOPINAE Miers. 



Ithizopidac .STIMPSON, Proc. Acad. Nat. Sci. Phila., vol. 10, 1858, p. 95 [41]. 

 Rhizopinae MIERS, Challenger Kept., Zool., vol. 17, 1SSG, p. 223. ALCOCK, 

 Jouru. Asiat. Soc. Bengal, vol. G9, 1900, pp. 287, 203, and 318. 



Eyestalks often fixed, corneae small or obsolete; the lower border 

 of the orbit has a tendency to run downwards toward the epistome. 

 The carapace usually has its antero-lateral corners cut away and 

 rounded off: the front may be square-cut and broad, or narrow and 

 more or less distinctly bilobed and deflexed. The antennules may 

 be of fair size and transversely folded, but more often, owing to 

 the narrowness of the front, they are cramped and fold obliquely; 

 sometimes they can not be folded in their fossae at all. Antennal 

 flagella usually short. The epistome may either be well defined and 

 prominent, or ill defined and sunken. The buccal cavern may be 

 squarish, but often diminished in breadth anteriorly; the external 

 maxillipeds have a square or suboval merus and may completely close 

 the buccal cavern, or there may be a gap between them. The male 

 abdomen does not nearly cover the space between the last pair of 

 legs. Male openings sternal. 



Only one genus, and that atypical, is found in American waters. 



Genus CHASMOCARCINUS Rathbun. 



Chasmocarcinns RATHBUN, Bull. Lab. Nat. Hist. State Univ. Iowa, vol. 4, 

 1898, p. 284 ; type, C. typicus Rathbun. 



Carapace thick, broadest posteriorly, tapering anteriorly to the 

 orbit and without lateral teeth. Fronto-orbital margin about half 

 the width of the carapace. Front narrow, bifid. Orbits small, deep, 

 .outer angle not prominent. Eyestalks small, tapering, movable. 

 The antennular cavities are entirely filled by the large basal joint. 

 The basal joint of the antennae is short and does not nearly reach 

 the front; flagellum of fair length. Inner orbital hiatus very broad. 

 Epistome projecting below the maxillipeds. Buccal cavity with 

 parallel sides. Maxillipeds standing wide apart, the merus as long 

 as broad, suboval, shorter than the ischium. Chelipeds unequal, fin- 



