410 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



Type locality: 1.5 miles northeast of Cape Pulmo, Lower California, 

 Mexico; 50 fathoms; Zaca station 136. 



Localities subsequently reported, ivith collectors: Gulf of California, 

 Mexico: Arena Bank, 35-45 fathoms, Zaca (Crane). 



Atlantic analogue: None. A Gulf of California endemic species. 



Diagnosis: Rostral horns straight, diverging widely; rostrum between 

 one-fourth and one-fifth length of carapace. Three lateral marginal 

 spines, one hepatic and two branchial. Five median dorsal spines. Basal 

 antennal article distally biconcave, median ridge spine-tipped, trending 

 obliquely forward and outward. Tip of male first pleopod elongated, 

 fleshy, recurving; keel erect, little broadened. 



Description : Carapace triangular-ovate ; regions tumid, covered with 

 thick, spongelike pubescence and groups of curve-tipped setae. Rostral 

 horns widely diverging, at an angle of nearly 78°, regularly tapering to 

 slender, slightly incurving tips. Supraorbital spine heavy, upturned ; pre- 

 orbital spine separated from supraorbital by a long narrow sinus. Median 

 spines five, the anterior very small, the rest large, stout, cylindrical, blunt ; 

 three large, conical, upward-pointing, lateral spines, the hepatic joined 

 to the smaller subhepatic by a ridge ; a pair of stout upward-pointing, 

 mesobranchial spines, one of them opposite the cardiac region ; forming, 

 with the proximal anterolateral spines and the cardiac spine, a transverse 

 line of five heavy spines across the carapace at this point ; the other bran- 

 chial spines with the median lateral spines forming a transverse row of 

 four spines across the carapace at the metagastric region. 



Chelipeds almost as long as first ambulatory leg; merus armed on 

 upper crest with four large spines and a distal lobe; carpus roughened 

 with a few low tubercles; manus long, cylindrical, tapering, armed with 

 a single proximally placed tubercle on upper margin ; fingers long, taper- 

 ing, slightly gaping proximally. Ambulatory legs stout, pubescent; dactyli 

 pubescent, curved. (Glassell, modified) 



In the largest specimen examined, a 36.2 mm female, the rostrum is 

 longer than in the holotype, being one-fourth, instead of one-fifth, the 

 total carapace length. There are but four median carapace spines rather 

 than five. A 29.2 mm male has but three median spines, the fourth being 

 represented by a tubercle. From the growth sequence in the related and 

 better known Stenocionops ovata, it may be concluded that the fourth 

 tubercle of the 29 mm specimen becomes the fourth spine of the 36 mm 

 specimen, while an inconspicuous fifth tubercle on the 36 mm specimen 

 might in time develop into the fifth spine of the 56 mm holotype. 



