44 BULLETIN 166, UNITED STATES NATIONAL MUSEUM 



Genus HYPOCONCHA Guerin 



Hypoconcha GufiRiN, Rev. Mag. Zool., ser. 2, vol. 6, p. 333, 1854 [type, H. 

 sahulosa (Herbst)]. — Bouvier, Bull. Mus. Hist. Nat., Paris, vol. 4, p. 374, 

 1898. 



Front and lateral margins expanded, covering the eyes and all 

 parts of the head except the flagella of the antennae; middle surface 

 very thin and membranous. Margin of anterior half usually hairy, 

 also the lower surface and appendages. The fourth and fifth pairs of 

 feet are prehensile without being subchelate; dactyl lunate. The 

 shape of the crab has been modified to suit its dwelling or protective 

 covering, for it carries over its carapace the valve of a lamellibranch, 

 holding on by some of its posterior feet and by the angular abdomen 

 inserted under the hinge. 



North Carolina to Brazil; Mexico to Peru. Africa (?). 



KEY TO THE SPECIES OF THE GENUS HYPOCONCHA 



A^ Merus of outer maxilliped subtriangular, its anterior border 

 longer than lateral border and as long as two preceding 



articles united californiensis (p. 51) 



A^. Merus of outer maxilliped trapezoid, its anterior border shorter 



than lateral and shorter than two preceding ai tides united. 



B'. Three large granulated tubercles forming a triangle on either 



side of ventral surface of carapace sabulosa (p. 44) 



B^. Not three large granulated tubercles on either side of ventral 

 surface of carapace. 

 C^ Distal end of merus of outer maxilliped swollen. A large 

 spine-tipped protuberance on either side of ventral surface 

 of carapace. Spines numerous, upwards of 25-- spinosissima (p. 46) 

 C^. Distal end of merus of outer maxilliped thin. 



D'. Granules of ventral surface of carapace more or less 



concealed by dense hair. 



E'. Manus with many longitudinal rows of granules and 



three granulate lobes near fingers; outer face of 



carpus bordered with hair below and at proximal 



end and with a raised, granulate line above panamensis (p. 47) 



E^. Manus with about 10 pointed and well-separated 

 granules through middle of outer surface; carpus 



with two distant spines arranged lengthwise lowei (p. 50) 



D^. Granules of ventral surface of carapace plainly visible, arcuata (p. 47) 



analogous species of hypoconcha on opposite sides of the continent 



Atlantic Pacific 



arcuata. panamensis. 



HYPOCONCHA SABULOSA (Herbst) 



Plate 8, Figures 3, 4; Plate 9, Figures 1-5 



Faux Bernard I'Hertnite P. Nicolson, Essai sur I'histoire naturelle de Saint- 

 Domingue, p. 338, pi. 6, figs. 3, 4, 1776. — Lamarck, Histoire naturelle des 

 animaux sans vertebres, vol. 5, p. 264, 1818. 



