PART 1 GARTH : PACIFIC OXYRHYNCH A 175 



Measurements: Largest specimen, a female from the Gulf of Cali- 

 fornia: length 25.9 mm, length posterior to gastric tubercle 14.8 mm, 

 width 16.0 mm, rostrum 3.8 mm, width 4.2 mm, cheliped 16.5 mm, chela 

 6.8 mm, dactyl 3.3 mm, height of palm 1.8 mm, ambulatory legs 27.0, 

 19.7, 16.8, and 13.5 mm, respectively. Male specimen: length 18.1 mm, 

 width 10.5 mm. 



Color in life: Carapace and chelipeds uniform Sudan brown, hand a 

 tone lighter, fading to very pale finger tips. Eyestalk amber; eye buff 

 yellow. Ambulatory legs lighter than carapace; nail of dactyl clear pale 

 amber. Ventral side raw Sienna. (Petersen, of an Isabel Island specimen) 



Habitat: Taken on rocky substrate and on sandy bottom four times 

 each, on coral and coralline bottom two times each, and on mud (with 

 sand) once. With Ulva, filamentous alga, coralline alga; hydroids, 

 sponges. 



Depth: Shore to 15 fathoms. To 29 fathoms. (Crane) 



Size and sex: Males in the present series are from 9.9 to 18.1 mm, 

 females from 7.5 to 25.9 mm, young from 5.5 mm. 



Breeding: The single ovigerous female was encountered by the 

 Velero III at Maria Magdalena Island, Mexico, in May. 



Remarks: From the material now available from the west coast of 

 Middle America, including that of the Askoy as well as that of the 

 Velero III, it is apparent that Bell's species, having Panama as its type 

 locality, is the true analogue of the Atlantic Tyche emarginata, and that 

 specimens from the Galapagos Islands, attributed by this writer (Garth, 

 1946, p. 406) to T. lamellifrons, are in reality a distinct and undescribed 

 species. The diagnosis and description of T. lamellifrons, as given by 

 Bell, A. Milne Edwards, and Rathbun, therefore, apply as before to 

 Pacific mainland specimens, while the diagnosis and supplementary de- 

 scription of T. lamellifrons given by Garth, as well as the published 

 figure (op. cit., pi. 54, figs. 1-6), apply to the Galapagos species instead. 



The best comparison between Tyche lamellifrons and T. galapagensis 

 is provided by a 25.9 mm female of the former from San Lorenzo Chan- 

 nel, Gulf of California, station 498-36, and the type specimen of the 

 latter, a 27.7 mm female from Albemarle Island, Galapagos. In the Gulf 

 of California specimen the rostral horns are long and exceed the pre- 

 orbital, while the length and breadth of the posterior medallion are 

 subequal. The ambulatory legs are much more slender than in the 

 Galapagos species, the cheliped being not noticeably more robust than 

 the walking legs. The maxillipeds are narrow, the ischium deeply 

 grooved, the basal projection of the exognath recurving to lodge itself 



