74 THE BRACHYURA. 
Mithrax bellii Gerstaecker. 
Mithrax ursus Bell, Proc. Zool. Soc. London, 1835, 3, 171, pub. Feb. 24, 1836; Trans. 
Zool. Soe. London, 1836, 2, 52, pl. 10, figs. 2 and 3. A. Milne Edwards, Miss. 
Sci. au Mexique, 1875, part 5,1, 103. Not Cancer ursus Herbst. 
Mithrax bellii Gerstaecker, Arch. f. Natur., 1856, 22, part 1, 112. 
Mithrax bellii Rathbun, Proc. Wash. Acad. Sci., 1902, 4, 284. 
Chatham Id., Galapagos; shore; Jan. 8, 1905; 1 ? juv. 
The young of this species, as Bell has shown, presents such a different 
aspect from the adult that it might easily be mistaken for another species. 
Length of young ?, Chatham Id., 21.7, width 20.7 mm. The body and legs, 
except the chelae, are everywhere covered with a furry hair. The protuber- 
ances are all sharp-pointed. The rostral horns curve toward each other; the 
pair of spines at the base of the horns are nearly as long as the horns and 
diverge from each other; the next pair is very small. In the adult (¢ from 
Black Bight) the carapace is wider than long (63.6 mm. long x 65.4 mm. 
wide), the surface is almost wholly naked, and the protuberances are very 
stout, blunt tubercles. 
Mithrax denticulatus Bell. 
Mithrax denticulatus Bell, Trans. Zool. Soc. London, 1836, 2, 54, pl. 11, fig. 2. 
Perico Id., Panama; Oct. 26, 1904; 1 ¢,2 °. 
Thoe erosa Bell. 
Thoe erosa Bell, Proc. Zool. Soc. London, 1835, 3, 171, pub. Feb. 24, 1836; Trans. Zool. 
Soc. London, 1836, 2, 48, pl. 9, fig. 4. A. Milne Edwards, Miss. Sei. au Mexique 
1875, part 5,1, pl. 19, fig. 4; 1878, p. 121. } 
Taboguilla Id.; between tide-marks; Oct, 31, 1899; 1. 
Perico Id., Panama; Oct. 26, 1904; 1 ¢. 
CALAPPIDAE. 
Calappa convexa Saussure. 
Calappa convexa Saussure, Rev. Mag. Zool., 1853, (2), 5, 362, pl. 13, fig. 3. 
Taboguilla Id.; shore; Oct. 28, 1904; 14. 
