512 BULLETIN 129, UNITED STATES NATIONAL MUSEUM 



rowed in front; completely closed by the external maxillipeds. Cheli- 

 peds usually of immense size and length, out of all proportion to the 

 short, slender ambulatory legs; arm and hand usually prismatic 

 with the borders strongly dentate; fingers much shorter than palm 

 and abruptl}^ curved inward and a little downward. (After Alcock.) 

 A large genus ranging from the continental slope off southern 

 New England to southern Brazil, from western Mexico to Panama 

 and Galapagos Islands, and throughout the Indo-Pacific region, the 

 Mediterranean sea and eastern Atlantic Ocean. 



KEY TO THE AMERICAN SUBGENERA AND SPECIES OF THE GENUS PARTHENOPE 



A'. Chelipeds more than twice as long as carapace. 



B'. Carapace ovate-pentagonal, surface little carinate in adult. 



Subgenus Parthenope, p. 513. 

 C^ Second segment of abdomen trilobed, lobes conspicuous in dorsal view. 



A slender spine at tip of rostrum agonus, p. 513. 



C-. Lobes or teeth of abdomen invisible in dorsal view. No slender spine at 



tip of rostrum hyponca, p. 514. 



B^. Carapace carinate or tuberculate, broadly triangular, with more or less 



rounded sides Subgenus Platylambrus, p. 516. 



C. Carapace and chelipeds very flat; spine at end of main, dorsal branchial 



ridge small serrata, p. 516. 



C^. Carapace ver}^ convex; spine at end of main, dorsal branchial ridge large. 

 Chelipeds not flat. 

 D'. Three larger tubercles on posterior margin, one of which is median. 

 E'. Carapace much broader than long. Manus with 8 to 10 teeth on 

 inner and 10 to 12 on outer margin. 

 F'. Inner oblique row of tubercles on branchial region depressed, 



situated in branchio-cardiac fossa pourtalesii, p. 521. 



F^. Inner oblique row of tubercles on branchial region elevated. 



exilipes, p. 523. 



E^. Carapace not much, if any, broader than long. Manus with few 



good-sized marginal teeth, 6 to 8 on inner, and 3 to 5 on outer 



margin fraterculus, p. 525. 



D^. Four larger tubercles on posterior margin, those of inner pair on each 

 side of middle. 

 E'. Carapace two-fifths broader than long. Marginal teeth elongate, 



subacute, spiniform depressiuscula, p. 524, 



E^. Carapace narrower, two-sevenths broader than long. Marginal 



teeth shorter, suboblong, blunt, lobiform guerini, p. 525. 



A^. Chelipeds less than twice as long as carapace, stout and contorted. 



Subgenus Pseudolambrus, p. 528. 

 B'. Antero-lateral margins oblique and nearlj^ straight, without distinct angle. 



Upper margins of palm 8- or 9-toothed triangula, p. 528. 



B^. Antero-lateral margins distinctly angled, the outer part parallel with axis 

 of body. Upper margins of palm respectively 4- and 6-toothed. 



excavata, p. 529. 



ANALOGOUS SPECIES ON OPPOSITE SIDES OF THE CONTINENT 



Atlantic Pacific 



pourtalesii. exilipes. 



guerini. depressiuscu la. 



