18 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



it not for the small holotype of M. p. plethodon and temporal con- 

 siderations of M. p. f rater, we would be prone to consider M. plethodon 

 as monotypic. The limited material of topotypic M. p. plethodon and 

 M. p. f rater, plus the fact that the latter is known only from frag- 

 mentary skulls, make assessment of the status of the Barbadian and 

 Puerto Rican subspecies extremely difficult. The geographic isolation 

 of Barbados from the balance of the Lesser Antillean chain and the 

 presence of an apparently isolated segment of M. p. plethodon in 

 Puerto Rico have been decisive factors in our retention of these 

 two populations as distinct from the main body of Lesser Antillean 

 M. p. luciae. Lack of presently demonstrable differences between 

 the populations of M. p. plethodon on the Lesser Antillean islands 

 of St. Lucia, Dominica, Antigua, Barbuda, and Anguilla suggests 

 that the species is relatively stable genetically (a suggestion somewhat 

 confirmed by the small differences among the subspecies M. p. 

 plethodon, M. p. luciae, and M. p. jrater), or that there is intercourse 

 between populations of M. p. plethodon on the various Lesser An- 

 tillean islands (although as yet Monophyllus remains unknown from 

 any two adjacent islands except Barbuda and Antigua on the same 

 bank), or that M. p. plethodon is a relatively recent arrival on at least 

 some of the Lesser Antillean islands, which it now occupies without 

 sufficient elapsed time for local subspecific differentiation. The latter 

 seems to us to be the most acceptable interpretation. Doubtless, 

 additional collecting will reveal the presence of M. plethodon on 

 at least those Lesser Antillean islands (Martinique, Guadeloupe, 

 and the islands of the Anguilla Bank) that lie either between known 

 stations of occurrence of the species or on the same bank as islands 

 from which M. plethodon is known. 3 The French islands in particular 

 are poorly explored mammalogically. 



The complete dichotomy of M. plethodon and M. redmani in the 

 one character that distinguishes them — the diastema between the 

 upper premolars — makes any analysis of relationships, history, and 

 loci of origin extremely difficult. The general concordance in size of 

 M. plethodon and M. r. redmani suggests that the latter is the subspecies 

 of M. redmani most closely related to M. plethodon. This indeed may 

 be the case, but M. r. redmani occupies that island (Jamaica) in the 

 range of the species that is farthest removed from the present distri- 

 bution of M . plethodon. Perhaps M. r. redmani was an early fortuitous 

 arrival in Jamaica from the Lesser Antilles. Data presented by 

 Koopman and Williams (1951), however, suggest that M. redmani 

 arrived relatively recently on Jamaica although Williams (1952) 



3 A'ter this paper was submitted for publication, a specimen of M. plethodon 

 was collected on St. Vincent by a field party from the Museum of Natural 

 History, University of Kansas. 



