76 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



of the postorbital tooth, is a character most useful in separating young 

 specimens with a bifurcate rostrum and smooth carapace from C. 

 tumidus. 



The fingers of the adult male gape more widely at the base than is 

 shown by Rathbun (1925, text-fig. 35a), a circumstance attributable 

 to the larger size of the Hancock specimen, which measures 26.2 mm 

 in length as compared to but 18.8 mm. 



Material examined: 92 specimens from 32 Hancock expeditions 

 stations, 20 of which were in the Gulf of California. (See Table 8) 

 From Cedros Island, west coast of Lower California, and Tepoca Bay, 

 Gulf of California, Mexico, to Sechura Bay, Peru. 



Measurements: Largest specimen, male: length 26.2 mm, width 

 21.1 mm, rostrum 2.0 mm, cheliped 37 mm, chela 16 mm, dactyl 8.1 

 mm, ambulatory legs 56, 50, 44, and 39 mm, respectively. Ovigerous 

 female: length 21.5 mm, width 18.1 mm. 



Color in life: Not recorded. 



Habitat: Bottom types at 26 stations on which information is 

 available show an overwhelming preference on the part of this species 

 for a sandy substratum, sand being recorded in 65 per cent of the cases, 

 with shell associated in 5 of 17 stations. The remaining 35 per cent 

 were divided as follows: mud 16 per cent, rock 12 per cent, and organic 

 bottom (coral and coralline) 8 per cent. Crane (1937) reported mud 

 and crushed shell bottom. 



Depth: Hancock expeditions specimens were obtained in from 3-90 

 fathoms. This is less than the extreme depth of 145 fathoms recorded by 

 Rathbun (1925, table, p. 111). 



Breeding: Ovigerous females were encountered in the Gulf of 

 California in January, February, and March, and from the west coast 

 of Lower California in March and April, but were not recovered from 

 any of the more southerly stations. 



Remarks: On the basis of the considerations mentioned in the 

 supplementary descriptive note above, Hancock expeditions specimens 

 from Panama, Colombia, and Ecuador, earlier catalogued as Collodes 

 tumidus, were clearly demonstrated to be C. tenuirostris instead. Of 

 considerable interest from the standpoint of geographical distribution is 

 the fact that C. tenuirostris, possessing an Atlantic analogue in C. 

 rostratus, is the species which might have been expected to occur in the 

 Bay of Panama. 



The range of the species is extended northward to Cedros Island, 

 west coast of Lower California, and southward to Sechura Bay, Peru. 



