324 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



oms, Albatross (Rathbun, 1898), Hassler, and C. R. Orcutt (Rathbun, 

 1925). "Lower California," T. H. Streets (Streets, as Libinia semi- 

 zonale) . 



Atlantic analogue: None. A west coast of Lower California species. 



Diagnosis: Carapace with 8 median and 2 hepatic spines. Rostrum 

 short, ascending, channeled beneath. Only one tooth on basal antennal 

 article. Manus of adult male not noticeably compressed, fingers gaping 

 narrowly. Tip of male abdomen triangular. Male first pleopod chan- 

 neled to tip ; keel of similar length, recurved, and setose. 



Description: Carapace broadly pyriform, its width less than the post- 

 frontal length. Rostrum ascending, not widened at the extremity, emargi- 

 nate, forming two shallow teeth shorter in old than in young; rostrum 

 arched from side to side, bordered with a fringe of hair, and forming 

 with the rather rigid, similarly fringed antennae, an expiratory channel. 



Median spines eight, four gastric, one genital, two cardiac, and one 

 intestinal ; a single spine on each side of the anterior gastric spine ; two 

 marginal spines, one branchial, the other subhepatic; four dorsal bran- 

 chial spines, two forming a slightly curved line with the marginal spine 

 and the posterior cardiac spine, and the other two in line with the 

 genital spine. A prominent preocular spine. Two hepatic spines, one 

 above the other; a subbranchial spine, below the epimeral suture. A 

 small spine or two on either side above the postlateral margin. Two stout 

 pterygostomian spines, the posterior one very blunt; a spine at antero- 

 external angle of basal antennal segment ; a spine just behind the outer 

 margin of that segment. 



Chelipeds of old male much longer than ambulatory legs, stout, finely 

 granulate ; palm not widening much toward fingers ; dactylus two-thirds 

 as long as upper margin of palm ; fingers gaping in basal half. Legs stout 

 and rather short. (Rathbun, 1925) 



Abdomen [of male] composed of seven segments; on the center of 

 the first segment a rather prominent tubercle; the terminal segment 

 somewhat triangular, with a rounded apex. (Streets, modified, of Libinia 

 semizonale) 



Male first pleopod channeled to tip, overlapping edges forming a 

 tubular extension of spermiducal canal; keel erect, narrowly triangular, 

 and, like tip, recurved and setigerous. In a 20.9 mm young male from 

 station 1031-40 the keel is not attenuated, nor are the sides of the 

 grooved tip overlapping. (See Plate T, figs. 2, 3) 



In the young, 18 mm or less in length, eleven spines are very long 

 and the rest small. The long spines are three median (penultimate gas- 



