ON THE SKULL AND AFFINITIES OF RANA SUBSIGILLATA, 21 



4. On the Skuli and Affinities oE Rana snhshjillala A. Duui. 

 By Miss Joan B, Procter, F.Z.S. 



[Received January 17, 1919 : Read Marcli 4., 1919.J 



(Text-figwms 1 & 2.) 



Whilst making a study of the osteological charactei-s in the 

 genus liana, it was pointed out to me by Mr. Bouleniger that 

 the skull of the West African liana sv^hsigillata A. Dum., to 

 which he was the first to draw attention *, might prove on closer 

 examination to be of such special interest as to justify a detailed 

 description, Mr. Boulenger, whom I have to thank for his kind- 

 ness in giving me every facility to make this study, regards this 

 frog as the monotype of a subgenus named by him Aiibria, In 

 his paper t, " Aper9u des principes qui doivent regir la classifi- 

 cation naturelle des especes du genre Rana,' some of the most 

 striking characters of thi.s ffogare briefly noticed, and its position 

 in the genus explained. 



On raising the scalp, for a superficial examination, the skull is 

 seen to appix>ach that of Rana [Fyscicej^halus) achpersa Tschudi 

 in several characters, v/hich will be enumerated later. It is 

 strongly ossified, rather depressed, and broader than long, the 

 general shape being typically frog-like. The iiaterorbital portion 

 of the brain-case is slender. Seen in profile, the cranium slopes 

 upwards from the nasal region to a point in line with the posterior 

 orbital borders, from which there is an abrupt decline to the 

 foravien magnum (see text-fig. 1 c). 



The membrane-bones op the cranium. 



The nasals are large, well-developed triangular bones, and 

 somewhat rugose. They meet each other in the median line 

 almost throughout their length, which is nearly two-thirds that 

 of the fronto-parietals. Anteriorly each is obtusely pointed ; 

 posteriorly they form short oblique sutures with the anterior 

 borders of the fronto-parietals, exposing in the centre a minute 

 diamond-shaped area of the ethmoid. The distal ends do not 

 reach the maxillje proper, although they rest upon the maxillary 

 processes in conjunction with the palatine cartilages. 



The vomers are oblique, presenting an acute angle backwards 

 and inwards, where they approach the proximal ends of the 

 palatines, and the pai-asphenoid. Anteriorly they are deeply 

 notched, the anterior processes reaching the maxillse. These 



* a R. Ac. Sci. Paris, 165. (1917) ix 987. 

 t Bull. Soc. ZooL France, xliii. 1918, 



