PART 1 GARTH : PACIFIC OXYRHYNCHA 399 



three on each side anteriorly, and a transverse row at the posterior end. 

 One tubercle on the genital region ; ten on the cardiac, two being median. 

 Posterior branchial region with several tubercles, the chief of these 

 arranged in two longitudinal rows; posterolateral angle with a spine 

 curving upward. A row of blunt tubercles above the posterior margin. 

 Margin of the hepatic region with only a small tubercle ; vertical side of 

 the branchial region with scattered tubercles, and two lines of tubercles 

 continued to the pterygostomian region. Anterior and lateral regions 

 hairy. Rostrum deflexed, with two flattened, triangular, acute horns, 

 pointing directly forward, and separated by a V-shaped sinus reaching 

 one-half the length of the rostrum. Preorbital tooth blunt, denticulate. 

 Two superior orbital fissures on either side of a rounded lobe ; postorbital 

 tooth blunt. The basal antennal article bearing at its anterolateral angle 

 a long, broad, blunt spine or tooth, curved inward and upward and with 

 crenulated outer margin; a short, blunt tooth at the base of the second 

 article; a tooth on the outer margin, forming part of the wall of the 

 orbit, and two laminate teeth between the outer sinus and the buccal 

 cavity. 



Chelipeds one and one-third times the length of the carapace in the 

 male. Upper surface of the merus and carpus with some scattered tuber- 

 cles; outer surface of merus with a longitudinal row; also two or three 

 tubercles at the proximal end of the outer lower margin. Palm long and 

 narrow, margins parallel, superior length twice the width and more than 

 one and a half times the length of the dactylus. Pollex not bowed down- 

 ward as in Microphrys platysoma Stimpson. The chelipeds of the female 

 differing in being more slender and about nine-tenths the length of the 

 carapace. First pair of ambulatory legs reaching half the length of the 

 palm of the chelipeds in the male and equaling the chelipeds in the 

 female. Merus of ambulatory legs armed with spines and tubercles on 

 the superior and outer or posterior surfaces; carpus with two or three 

 spines; margins hairy. (Rathbun, 1898, modified) 



Material examined: 166 specimens from 34 stations. (See Table 83) 

 From Dewey Channel, west coast of Lower California, and from An- 

 geles Bay, Gulf of California, Mexico, to Santa Elena Bay, Ecuador, 

 including Cocos Island, Costa Rica. 



Measurements: Largest specimen, male: length 23.0 mm, width in- 

 cluding spines 19.0 mm, width without spines 18.5 mm, rostrum 3.1 

 mm, width 2.7 mm, cheliped 34.0 mm, chela 17.8 mm, dactyl 8.0 mm, 

 height of palm 5.8 mm, ambulatory legs 23.6, 19.8, 17.1, and 14.5 mm, 

 respectively. Female specimen: length 17.2 mm, width including spines 

 15.0 mm, width without spines 12.8 mm. 



