368 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 21 



Measurements: Largest specimen, female: length 20.0 mm, width 

 including spines 17.2 mm, without spines 14.7 mm, rostrum 4.5 mm, 

 width 2.5 mm, cheliped 17.5 mm, chela 7.6 mm, dactyl 3.3 mm, height 

 of palm 2.0 mm, walking legs 21, 19, 18, and 15 mm, respectively. Male 

 specimen: length 14.8 mm, width including spines 11.0 mm, without 

 spines 9.6 mm. 



Color in life: Carapace and chelipeds violet pink; ambulatories faintly 

 pink above; ventral surface grayish white. (Crane) See also Garth 

 (1946, p. 389). 



Habitat: Sandy mud. (Bell) Sand and rock; in a piece of coral 

 (Pocillopora ligulata) ; muddy bottom. (Crane) Sand, sand and shell, 

 and "rock, coral, nullipore, and bryozoa." (Garth) 



Depth: Shore to 50 fathoms; in the Galapagos Islands to 160 fath- 

 oms. 



Size and sex: It would be necessary to gather together in one place 

 all specimens extant of which measurements are known in order to have 

 a representative series. Males would measure 8 mm (Sivertsen), 10.1 

 mm (Crane), 11.3 mm (Garth), 13 mm (Rathbun), 14.8 mm (above), 

 and 16.2 mm (Glassell) ; females 17.5 mm (Crane) and 20.0 mm 

 (above). 



Breeding: An ovigerous female is yet to be recorded. 



Remarks: From a consideration of specimens examined and those 

 described in the literature it is apparent first, that Mithrax (Mithrax) 

 spinipes is based upon immature specimens, and second, that Galapagan 

 and mainland material, here united for convenience and because of the 

 general similarity of all mithracine young, is not strictly comparable 

 and may require separation as adults of the two forms become known. 

 To which group to refer the 6 mm male from Cocos Island is prob- 

 lematical at present. The inference in Garth (1946, p. 391) that M. 

 (M.) spinipes might be the young of M. CM.) orcutti Rathbun, here 

 considered a synonym of M. (M.) armatus Saussure, is invalidated by 

 the discovery of the distinctive young of the latter species. 



Mithrax (Mithrax) belli Gerstaecker 



Mithrax ursus Bell, 1835b, p. 171; 1836, p. 52, pi. 10, figs. 2, 2c-e, 3. 

 White, 1847, p. 7. A. Milne Edwards, 1875, p. 103. Miers, 1886, 

 p. 86. (Not Cancer ursus Herbst.) 



Mithrax bellii Gerstaecker, 1857, p. 112. Rathbun, 1902b, p. 284; 1907, 

 p. 74; 1910, p. 574; 1924b, p. 153. 



