550 BULLETIN 129, UNITED STATES NATIONAL MUSEUM 



at either angle. Ridge between subhepatic and afferent channels 

 minutely crenulate, pubescent, continued on subbranchial region with 

 several beadlike tubercles; suborbital tooth strongl}^ ridged. 



First segment of male abdomen very short; second widest, with a 

 transverse denticulate crest, a larger denticle at extremities and 

 middle; third, fourth, and fifth segments fused; sixth wider than 

 long; seventh very short, triangular; abdomen and sternum smooth. 

 Seven separate segments in female abdomen, first almost concealed 

 by carapace, second having a transverse denticulate crest, third with 

 a similar faint crest not continued to margins. Basal antennal joint 

 with a long trigonal spine below. Ischium of maxillipeds punctate, 

 outer margin pubescent, inner margin crenulate; merus with anterior 

 margin concave, surface pubescent, uneven, an oblique groove running 

 forward and outward, two tubercles on outer side of groove, one at 

 antero-external angle; inner angle strongly produced, bearing a 

 granulate ridge. 



Chelipeds over twice as long as carapace, strong; merus trigonal, 

 margins irregularly dentate or crenulate; carpus somewhat four-sided, 

 margins finely denticulate or crenulate, a ridge across lower surface; 

 hand long, trigonal, pubescent, upper surface slightly twisted, about 

 10 teeth on inner and on lower margin and 13 smaller teeth on outer 

 margin; dactyl at right angles to upper surface of palm, a large white 

 bead tubercle on outside of base. Legs compressed; merus, carpus, 

 and propodus with cristate margins. 



Measurements. — Female (17370), length of carapace 15.5, width of 

 same 21, length of cheliped about 33 mm. 



Range. — ^Lower California, outer side, from Abreojos Point south- 

 ward; Gulf of California; Panama Bay. Depth, 9J^ to 71 fathoms. 



Material examined. — See table, page 551. 



Genus AETHRA Leach 



Mthra Leach, in Latreille, Nouv. Diet. Hist. Nat., vol. 4, 1816, p. 602; 



type, A. scruposa (Linnaeus). 

 (Ethra Lamarck, Hist. Nat. Anim. sans Vert., vol. 5, 1818, p. 264. — Milne 



Edwards, Hist. Nat. Crust., vol. 1, 1834, p. 370. 



Carapace oval and embossed, circumference dentate, a little 

 raised and expanded so as to cover the ambulatory legs. Eyes very 

 small, orbits cu-cular. Basal article of antennae elongate, joined to 

 the front by its inner angle; flagellum small, situated in the orbital 

 hiatus. Basal article of antennules wide and almost quadrilateral. 

 Buccal cavity narrowing anteriorly, epistome short. Outer maxilli- 

 peds very long; merus truncate anteriorly and outside, and without 

 emargination for the insertion of the palpus. The legs can be en- 

 tirely concealed under the carapace; they are compressed and have 

 cristif orm ridges. Abdomen of male composed of five segments, female 

 of seven segments. 



