THE SPIDER CRABS OF AMERICA 461 



Measurements. — ^Largest male (16070), length of carapace from 

 tip of rostrum to posterior median spine tip 93, width including 

 spines 83.3, width excluding spines 77.7, length of rostrum 7. 8 mm. 



Range. — Gulf of California and Bay of Panama. Depth, 33 to 

 145 fathoms. 



Material examined. — See table, page 462. 



STENOCIONOPS TRIANGULATA (Rathbun) 



Plate 165, fig. 1; plate 266, fig. 1 



Pericera triangulata Rathbun, Proc. U. S. Nat. Mus., vol. 15, 1892, p. 246, 

 pi. 32, fig. 1 (type-locality. Gulf of California, 29 fathoms; female holo- 

 type. Cat. No. 16066, U. S. N. M.). 



Stenocionops triangulata Rathbun. Proc. U. S. Nat. Mus., vol. 21, 1898, p. 

 577. 



Diagnosis. — Median spines 9; none on posterior margin. One 

 hepatic spine. Rostrum about one-sixth length of carapace. 



Description of largest specimen. — Known only from small and imma- 

 ture specimens. Carapace triangular-ovate, broader behind in the 

 largest specimen, male, than in the female figured. Median spinej 

 9, distributed as in macdonaldi, none on the posterior margin; spines 

 unequal, the largest are the anterior cardiac, the two posterior, and 

 the penultimate gastric. Lateral marginal spines 3, large, 1 hepatic 

 (hepatic region not enlarged), 2 branchial, of which the spine at the 

 postero-lateral angle is the largest and points obliquely backward. 

 From it a curved line of 6 tubercles and spinules stretches to the 

 hepatic region. Two large spines on the elevated portion of the 

 branchial region; a low spine in front of each; a spine on either side 

 of the anterior median spine. 



Rostral horns widely divergent, at nearly a right angle, regularly 

 tapering to slender tips. Orbital spines narrow. Basal antennal 

 article 2-spined on anterior margin. 



Measurements. — Immature male, largest specimen (21940), length 

 of carapace from tip of rostral horn to tip of posterior median spine 

 30, width of carapace including spines 22.5, excluding spines 18.6, 

 length of rostral horn 5.3 mm. 



Range. — West coast of Lower California; Gulf of California; Bay 

 of Panama. Depth, 133^ to 513^ fathoms. 



Material examined. — See table, page 462. 



Remarlcs. — The surprising changes in form and ornamentation 

 between the young and the adult of S. spinimana — that is, the gradual 

 development from the typical Stenocionops form of the young into 

 the rotund Lihinia-like form of the adult, with hepatic regions sep- 

 arately distended and produced, the narrowing of the orbital region, 

 the shortening of the rostral horns, and the multiplication of spines — 

 5487— 25t 31 



