PART 1 GARTH : PACIFIC OXYRHYNCHA 243 



it as a new species, especially in view of the fact that E. trifurcatus and 

 E. rathbunae are known from the female sex only. In due time males 

 of these species will be recognized, and relationships, including possible 

 synonymy of the Galapagos form, may be straightened out with the help 

 of sexual characters, including the male pleopod. 



The writer departs from his previous concept of the morphology of 

 Stimpson's species, which is expressed in Rathbun's 1925 key and diag- 

 nosis: namely, the presence of a small tooth on the lateral margin be- 

 tween the hepatic and branchial lobes. A careful reading of Stimpson's 

 description, above, will reveal that this was not intended. The "tubercle 

 near the posterolateral angle" is shown in Plate N, fig. 1, and lies median 

 to the branchial lobe. The "small tooth on the lateral margin behind the 

 anterolateral angle" is the branchial lobe itself, which is otherwise unac- 

 counted for in Stimpson's description. With this point settled, other 

 slight discrepancies between the Manta specimen and the original descrip- 

 tion are matters of degree rather than of kind, and are to be accounted 

 for by variations of age, which in this species can be expected to parallel 

 those of E. peruvianus. 



As compared with the Manta specimen, the specimen from Acapulco, 

 an ovigerous female, differs in the following particulars: the rostrum is 

 shorter, and there is a distinct preorbital lobe. The branchial and hepatic 

 lobes are more slender and forward pointing. The anterior border of the 

 merus of the third maxilliped is convex, rather than concave. It will be 

 noted that in these particulars it approaches more closely Eupleurodon 

 peruvianus, and particularly the female figured by Rathbun (1925, pi. 

 49, figs. 5, 6), although the rostrum is less deeply incised. The female 

 specimen from Cabeza Ballena, which is within sight of Stimpson's type 

 locality, Cape San Lucas, also has the rostrum shorter, with a pronounced 

 preorbital swelling, rather than a lobe. In it the anterior margin of the 

 merus of the third maxilliped is also convex. These specimens were ob- 

 tained in formalin washings of algae collected by E. Yale Dawson. All 

 legs are detached from the carapaces, and it cannot be stated with cer- 

 tainty that the legs present belong to the specimens described. 



Eupleurodon peruvianus (Rathbun), new combination 

 Plate O, Fig. 9 ; Plate 26, Fig. 6 



Eupleurodon trifurcatus, Rathbun, 1910, pp. 535, 572 (part: the Peru- 

 vian specimen), pi. 49, fig. 5. (Not E. trifurcatus Stimpson.) 



Epialtus peruvianus Rathbun, 1923a, p. 72; 1925, p. 157, text-figs. 53i, 

 58. Not Finnegan, 1931, p. 620. 



