PART 1 GARTH : PACIFIC OXYRHYNCHA 219 



Habitat: Almost always on muddy bottoms. (Crane) Sand, mud and 

 sand. (Garth) The 7 Velero III stations for which information on bot- 

 tom type is available break down as follows: coralline, 3 stations; rock 

 with sand, sand, mud with shell, and mud with rock, one station each. 



Depth: Velero III specimens were dredged in from 30-90 fathoms, 

 the latter record depth in the northern part of the Gulf of California. 



Size and sex: By referring again to material from off Daphne Minor 

 Island, Galapagos, station 792-38, it is possible to illustrate growth, be- 

 ginning with a young specimen of 2.3 mm and continuing through stages 

 of 5, 7.5, and 9.5 mm. The 2.3 mm specimen is 1.8 mm wide and its 

 rostrum but 0.4 mm in length. The short horns are acute and widely 

 divided, the three lateral lobes little more than blunt spines, and the 

 enlarged eye gives it much the appearance of a young Mithrax at this 

 stage. By 5 mm the inner margins of the rostral horns are beginning to 

 converge and the outer margins curve broadly inward. In the 7.5 and 

 9.5 mm stages the rostral development continues, along with that of the 

 lateral lobes ; but the rostrum is not so lengthy, nor the posterior of the 

 lobes so protuberant, that the triangular or pyramidal shape of the cara- 

 pace is lost. 



A young female specimen from north of San Pedro Nolasco Island, 

 Gulf of California, station 572-36, also 9.5 mm in length, shows much 

 of the anterior portion of the carapace punctate and setose. The rostrum 

 is most heavily pitted, and in each minute depression there grows either 

 a short clavate seta or a tiny vesicle. The punctae are continued down a 

 median ridge onto the anterior gastric region and on the outer hepatic 

 and branchial regions. The actual margins of the anterolateral lobes, as 

 well as the inner branchial and cardiac regions, are smooth and bare. 



In the adults, the difference in relative length and width of male and 

 female is accounted for by the relatively longer rostrum of the male. 

 The measurements above also show that the male cheliped does not 

 become massive, and that the first walking leg in the male is considerably 

 longer than the remaining legs. 



The largest specimen on record is the 39 by 28 mm male from Bay 

 of Panama (Faxon). 



Remarks: For a second time the young of this species were taken on 

 an echinoderm. In the Galapagos Islands it was a holothurian (cf. 

 Garth, 1946, p. 379) ; in the Gulf of California specimens were removed 

 from the dried test of Stylocidaris perplexa, an echinoid. 



Sphenocarcinus agassizi is now recorded from the Central American 

 mainland at Bahia Honda, Panama. Its vertical range is extended to 90 

 fathoms. 



