638 



PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 118 



specimens examined by him from the Galapagos Islands exhibited 

 "almost infinite variation." This variabiHty is especiaUy discon- 

 certing in the form of the meriis of the outer maxillipeds ; that segment 

 may be either subquadrate or markedly produced at the distolateral 

 angle in specimens from the same general area. On the other hand, 

 the prolongation of the posterolateral angles of the penultimate 

 abdominal somite of the male and the form of the gonopods seem to 



b 



Figure 1 —Micropanope melanodactylus, laterocephalic aspects of right gonopods: a, 

 homoeotype with carapace length of 6.1 mm. from roadstead of Porto Grande, St. Vincent' 

 b, syntype of Micropanope polita with carapace length of 5.3 mm.; c, syntype of Panopeus 

 tanneri with carapace length of 6.0 mm. 



be reliable diagnostic characters. Intensive study of material from 

 the eastern Atlantic and the eastern Pacific may eventually disclose 

 dift'erences of subspecific importance, but it seems best for the present 

 to consider the two populations identical. 



It is remarkable that this species, which is abundant in the eastern 

 Atlantic and the eastern Pacific, is apparently absent from the western 

 Atlantic. None of the species described from eastern America have 

 gonopods that could be confused wdth those of M. melanodactylus. 

 M. truncatifrons Rathbun, 1898, which is known from only two fe- 

 males and one juvenile from off Cuba and off Yucatan, bears a 

 superficial resemblance to M. melanodactylus, but I beheve that it is a 

 distinct species; in both adult females, the front is straighter, the 

 outer surfaces of the pahns are more completely granular, and the 

 color on the fingers is less extensive than in any specimens of M. 

 melanodactylus examined. 



I agree mth Monod (1956, p. 324) that M. melanodactylus is prob- 

 ably not a synonym of Xantho minor Dana, 1852b. Unfortunately, 

 the type-specimen of Dana's species is probably no longer extant, and 

 his name is therefore likely to remain a nomen duhium indefinitely. 



