76 BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



chelae are more slender than usual; (2) in the curvature and length 

 of the dactyl of the second leg, normally strongly curved like the 

 first and third but sometimes less curved and correspondingly 

 elongate. This straightening and elongation may occur on one or 

 both sides of a specimen and on one or several specimens from a 

 single gathering. 



Color. — Female, obscure brownish, immaculate; male, above black 

 with whitish spots, beneath yellowish-white. For exceptions see 

 above under variations. 



MeasureTRents. — Female (42850), length of carapace 13.7. width 

 of same 14.3 mm. Male (18014), length of carapace 8.4, width of 

 same 8.1 mm. 



Habitat. — Males often and young of both sexes usually free- 

 swimming. Mature males and females commensal in mussel {Mytllus 

 edulis), horse mussels {Modiola modiolus and M. tulipa), "long" 

 clam {Mya arenaria), scallops {Pecten irradians and P. tenuicostatus) 

 oyster {teste Blackford), Pinna muricata, and in tubes of annelid 

 {Chaetopterus pergamentaceus) . On muddy bottoms of bays and 

 sounds (Verrill). 



Range. — Cape Cod to Texas; Cuba; Jamaica; St. Thomas. Sur- 

 face to 21 fathoms. 



Material examined. — 



Off Marthas Vineyard, Massachusetts; Katama Point, E. | S., 

 IJ miles; 5 fathoms; S.; temp. 62° F.; Sept. 6, 1883; station 1172: 

 steamer Fish Haiok; 1 female (3G900). 



Woods Hole, Massachusetts; U. S. Fish Comm.: 1876; V. N. Ed- 

 wards; 1 y. (4082). Surface; Oct. 21, 1881; V. N. Edwards; 26 

 males and females y. (15022). Aug. 9, 1882; 1 male (40805). Aug. 

 12, 1882; 1 female y. (40804). Sept. 15, 1882; 1 male. 1 female y. 

 (40806). Surface; Sept. 17, 1882, evening; 1 male (12561). Sur- 

 face; Oct. 2, 1882, 8 p. m.; 1 female y. (12560). Surface, by electric 

 light; Aug. 5, 1885; 24 males and females y. (10917). Surface, by 

 electric light; August, 1885; steamer Albatross; 1 male y., 4 females 

 y. (11184). 1885; 1 female ovig. (34919). From Mya arenama; 

 Aug. 26, 1886; 1 y. (11840). Mar. 28, 1888; V. N. Edwards; 1 female 

 (26106). V. N. Edwards; 1 female .ovig. (3818). From mussel; 

 5 females (26140). Surface; Oct. 13, 1892; V. N. Edwards; 3 males, 

 5 females y. (49211). 



Woods Hole, Massachusetts; from tubes of Chaetopterus ; G. M. 

 Gray; 3 females (42148). 



Vineyard Sound, Massachusetts : Surface ; Aug. 29, 1882, evening; 

 U. S. Fish Comm.; 1 female y. (40808). Gay Head Light, W. f S., 

 2i miles; 10 fathoms; S.; temp. 60° F.; July 20, 1881; station 928; 

 steamer Fish Uawk; 22 males (of 2 sorts), 33 females (9 ovig.) 

 (19024,41032). 



