CALIFORNIA STALK-EYED CRUSTACEA. 97 



Subfamily ASTHENOGNATHIN^. 



External maxillipeds with both ischium and merus well developed. Last 

 pair of ambulatory legs not rudimentary or abortive. 



Genus Opisthopus Rathbun. 



" Carapace usually firm and unyielding; smooth, subquadrilateral, 

 regions not defined; lateral margins regularly arcuated. Epistome very 

 short. Abdomen seven-jointed, in the male not covering the sternum 

 between the coxa9 of the last pair of ambulatory legs. Eye-peduncles 

 short. Antennge small, situated at the inner orbital hiatus; basal joint 

 small. Antennulae obliquely plicated. External maxillipeds with the 

 ischium well developed, the merus broad, the palpus three-jointed, the 

 ultimate joint articulated on the inner side of the penultimate. Chelipeds 

 moderate; ambulatory legs subequal in length, joints flattened." 



Type. — 0. transversus Rathbujst. 



Opisthopus transversus Rath. 



Opisthopus transversus Eathbun M., Proc. U. S. Nat. Mus., Vol. XVI, 

 1893, p. 252. 



Carapace thin, convex, transverse. Front deflexed, with a slight median 

 sulcus. Ischium of the maxillipeds broad; merus as broad as long, with 

 the antero-external angle broadly rounded; palp large, last joint " narrow, 

 inversely spatulate, overreaching the penultimate joint. Chelipeds rather 

 stout; merus broad, trihedral; palm a little longer than the fingers, thick, 

 slightly compressed, margins rounded, lower margin convex." Ambula- 

 tory legs similar; second pair longest; fourth pair shortest; dactyls small, 

 curved, little more than half the length of the propodi. 



Length of Carapace. Width of Carapace. 



Male 8.5 mm 9.8 mm. 



Female 11 mm 13 mm . 



" 14 mm 18 mm. 



Monterey and Point Loma (Miss Rathbun). One 

 male from the shell of Lucapina crenulata Sowerby from 

 Monterey. San Diego! 



