70 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 5 



it as in the adult. This difference between the surface structure of juve- 

 niles and adults accounts for the peculiar features of the latter. As an 

 example, the merus of the chelipeds in the smaller specimens is heavily 

 eroded, and these same surfaces in larger specimens have the appearance 

 of scar tissue. 



Range: From Cape San Lucas, Baja California, Mexico, to Colombia, 

 and the Galapagos Islands. 



Material examined: Octavia Bay, Colombia, January 28, 1935, 

 shore; one female. Secas Islands, Panama, January 29, 1935, shore; tw^o 

 juvenile males. Bahia Honda, Panama, March 10, 1933, tw^o fathoms; 

 one male, juvenile. Playa Blanca, Costa Rica, February 8, 1935, shore; 

 three adult males, three juvenile males, and one juvenile female. Sulivan 

 Bay, James Island, Galapagos (see Type), also from same location, De- 

 cember 13, 1935, shore; one adult male. Charles Island, Galapagos, De- 

 cember 5, 1934, shore; one adult female. All the above specimens were 

 collected by the Allan Hancock Expeditions of the various years men- 

 tioned. 



Off the Nicaraguan Coast, lat. 12° 48' N., long. 87° 06' W., Feb- 

 ruary 3, 1939, twelve fathoms; one adult male; collected by Captain 

 Fred E. Lewis on the yacht Stranger. 



Cape San Lucas, Baja California, Mexico, shore; February 1, 1938; 

 one adult male ; collected by the author. 



Habitat: From the lower tidal regions, among rocks, to a depth of 

 twelve fathoms. 



Remarks: This proposed species has an affinity for D. semicircularis 

 (Flipse), 1930, but differs from that species in that the dorsal edges of 

 the meri of the ambulatory legs are overlapping instead of being more 

 or less entire. I have not seen a specimen of D. semicircularis, but through 

 the kindness of Dr. Edmondson and Dr. Bryan of the Bishop Museum, 

 Hawaii, I examined two specimens of D. horrida (Linn.) from that lo- 

 cation, and this proposed species differs from D. horrida in that the 

 sternal pit is semioval instead of broadly triangular, the posterolateral 

 margins forming a straight line with the posterior margin instead of 

 being oblique to this margin. To Dr. Fenner A. Chace, of M.C.Z., I am 

 indebted for comparisons and literature. 



This species is named for Mr. John S. Garth of the Allan Hancock 

 Foundation, in appreciation of his having allowed me to describe this 

 species and to examine the materials at his disposal. 



The accompanying drawings are not of the holotype. 



