134 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 8i 



record of this Gold Coast (type locality, Keta) species of which 

 aequiplicata Werner, of the Cameroons and Congo, is a synonym 

 according to Nieden, who made direct comparison of the types. 



The specimen comes from the Firestone Plantation No. 3, on the Du 

 River, Liberia, where it occurs together with R. maccarthyensis 

 (M.C.Z. Nos. 24462-3), R. o. griUnguiensis (M.C.Z. Nos. 24458-60), 

 R. o. oxyrhynchus (M.C.Z. Nos. 24455-7), and R. m. mascareniensis 

 (M.C.Z. Nos. 11927-31), the latter having been erroneously recorded 

 under the name bibronii in 1930. 



In view of the remarkable similarity of all these frogs and the 

 consequent difficulty of distinguishing them, it seemed advisable to 

 draw up the following key after a careful examination of Dr. Mann's 

 material together with that in the Museum of Comparative Zoology. 



1. A conspicuous transverse fold connects posterior edges of upper 



eyelids ; toes webbed to tips ; habit robust 2 



No transverse fold across crown of head ; habit more or less 



slender 3 



2. "Vomerine teeth in two oblique rows, anteriorly touching inner 



posterior edge of choanae, posteriorly converging ; snout acumi- 

 nate, as long as, or almost as long as, orbital diameter; tym- 

 panum sharply distinct, large, its diameter almost that of 



orbit ; tips of toes not dilated, at most thickened occipitalis 



Vomerine teeth (absent in young) in two round groups between, 

 but posterior to an imaginary line connecting hind edges of, 

 choanae ; snout rounded, once and a half as long as orbital di- 

 ameter ; tympanum indistinct, small, its diameter about a third 

 that of orbit; tips of toes dilated into distinct, though small, 

 disks c. alleni 



3. Vomerine teeth in two oblique rows between, though not in contact 



with, choanae ; tips of fingers and toes dilated into distinct disks. 

 Fourth toe with only 1 phalange free of web (or which may 

 be continued up it as a narrow seam to disk), remaining 

 toes webbed to base of their disks; tibiotarsal articula- 

 tion of adpressed hind limb reaches eye or just beyond 

 end of snout; vocal sacs of $ internal, but a glandular 



swelling present at base of forearm in ^ 5 a. albolabris 



Vomerine teeth in two rows projecting inward from anterior 



edges of choanae ; tips of fingers and toes simple, not dilated 4 



4. An inner and an outer metatarsal tubercle, latter connected by 



a series of minor tubercles with first subarticular tubercle of 



fourth toe. 



Fourth toe with 2 (rarely 3) phalanges free of web, first 

 toe with IVz (rarely 1 or 2), second with 1 (rarely ly^), 

 third with 1 (rarely 2), fifth with % (rarely 1 or lYz) 

 phalanges free of web; tibiotarsal articulation of ad- 

 pressed hind limb reaches nostril or well beyond end of 

 snout; vocal sac of $ external, its aperture extending 



posteriorly toward lower insertion of forearm maccarthyensis 



An inner metatarsal tubercle only, no minor tubercles on basal 



phalange of fourth toe 5 



