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 coxae of the last pair of ambulatory legs. Eye-peduncles 

 short. Antennae 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 BATHBCTN. 



Opisthopus transversus Rath. 



Opisthopus transversus KATHBUN 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 autero-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 Lorna (Miss Rathbun). One 

 male from the shell of Lucapina crenulata Sowerby from 

 Monterey. San Diego! 



