360 



BULLETIN 97, UNITED STATES NATIONAL MUSEUM. 



along the mesogastric region. The fine graniihited marginal line 

 in the male runs about one-third or less of the length of the lateral 

 border; in the female and young this edge is longer, sharper, and 

 denticulate. 



Fronto-orbital width in the old male about one-third, in the adult 

 female about nine-twentieths, of the width of the carapace. Front 

 widening distinctly below, lower edge strongly projecting, granulate, 

 slightly curved. Height of orbit about three-fourths of its width. 



The outer maxillipeds may reach the epistome in old specimens, 

 but fall short of it in smaller specimens; the gape is large, the line 

 between ischium and merus almost transverse, the merus suboblong, 

 with a -shaped notch in the rounded oblique distal extremity. 



Chelipeds unequal in both sexes but most of all in the male. Wrists 

 rather feebly spinulous or unarmed along the inner margin; larger 



palm of adult male much swollen, becoming 

 elongate with age, fingers very rough, gaping. 

 Legs shorter, broader, and rougher than in 

 ■ruricola, the merus joints distinctly mar- 

 gined above. Dactyli armed with 6 rows of 

 spines. 



Abdomen of male much wider than in 

 ruricola, except the last segment, which is 

 suboblong and half as wide as the preceding 

 segment. 



Measurements. — Male (20650), length of 

 carapace TO, width of same 104 mm. Female 

 (1964G), length of carapace 57.4, width of 

 same 75.3 mm. 



Ilahitat. — On the Tres Marias we found 

 them only on Maria Cleofa, where they were 

 very numerous above high-water mark on the sandy beaches of 

 the low eastern part of the island. They were also living very 

 abundantly in burrows in the soft soil almost ever3'where on the 

 slopes of Isabel Island. They are nocturnal in habits and caused 

 UP some annoyance by walking over us at night while we were 

 camped in their haunts. They began to come out of their bur- 

 roAvs as soon as it became twilight in the evening. In both localities 

 most of their burrows were found among the scrubby bushes. On 

 Isabel Island they were often seen during the day sitting in the bur- 

 row a foot or so from the entrance, but scuttled back to a safe depth 

 when I approached too near. (Nelson.) 

 Range. — "West coast of Mexico and adjacent islands. 

 Material examined. — 



Lower California; L. Diguet, collector; 1 male, holotype of G, 

 digueti (Paris Mus.). 



FlO. 103. — G ECAHCINUS 

 PLANATUS, ADDOME.X OP 

 MALE (20G50), NATURAL 

 SIZE. 



