74 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



Material examined ~by Prof. S. I. Smith. Pearl Islands, Bay of 



Panama, in Lithodomus (now Lithophagd] aristatus Forbes and 



Hanley which was in its usual habitat, an excavation in the shell 



-of a Spondylus; F. H. Bradley coll.; 1 female ovig., holotype 



(P.M.Y.U.). 



MUSSEL CRAB. 

 Plate 17, figs. 3-6. 



Pinnotheres maculatum SAY, Journ. Acad. Nat. Sci. Philadelphia, vol. 1, 

 1818, p. 450 (type-locality, "inhabits the muricated Pinna of our 

 coast"; cotypes, male and female, in British Mus.). 



Pinnotheres maculatus VERRILL, Kept. U. S. Commr. of Fish and Fisheries, 

 vol. 1, 1871-1872 (1873), pp. 309 [151, 434 [140], 459 [165]. SMITH, 

 Kept. U. S. Commr. of Fish and Fisheries, vol. 1, 1871-1872 (1873), 

 p. 546 [252]. FAXON, Bull. Mus. Comp. Zool., vol. 5, 1879, p. 265, 

 footnote (Zoea). FOWLER, Ann. Rept. New Jersey State Mus., 1911 

 (1912), p. 435, pis. 136 and 137; not (?) P. byssomiae De Kay and 

 Gibbes. 



Pinnotheres ostreitm SMITH. Rept. U. S. Commr. of Fish and Fisheries, 

 vol. 1, 1871-1872 (1873), p. 546 [252], part: pi. 1, fig. 2 (male) ; not 

 P. ostreum Say. 



Diagnosis. Dactyli of first 3 legs hooked, of fourth nearly 

 straight. Males usually, and the young always dark with light 

 spots. Female with shell thick, not yielding. 



Description of adult female. Surface covered with a short, dense, 

 deciduous tomentum. Carapace subcircular, little broader than long, 

 thick and firm but not hard, convex, uneven, smooth, the gastro- 

 cardiac area higher and separated by depressions from the branchio- 

 hepatic area; antero-lateral angles a little prominent; front slightly 

 advanced, about one-fifth width of carapace, in dorsal view sub- 

 truncate, bilobed by a shallow sinus, edge bent down to form a 

 triangular lobe in front view. Orbits small, subcircular; eyes 

 spherical. Antennae as long as width of orbit. Antennulae large, 

 obliquely transverse. 



Propodus of outer maxilliped larger than carpus and about twice 

 as long as wide; dactylus narrow-spatulate, curved, attached near 

 middle of propodus and reaching to extremity of the latter. 



Chelae of moderate size, smooth, hairy inside; carpus elongate; 

 palm thick, blunt-edged, increasing distally; fingers stout, fitting 

 close together, tips hooked; propodal finger nearly horizontal: dac- 

 tylus with a tooth near base fitting into a sinus of the fixed finger, 

 sinus with a small tooth at either end. 



Legs slender, smooth, hairy below, second pair longest, shorter 

 than cheliped, first three dactyli falcate, shorter than their respective 



