THE SYSTEMATIC VALUE OF RANA CHTNENSIS OSBECK 73 



foremost end, consequently, never extending into the orbit. This 

 is also the reason why the posterior corner of the inner branch of 

 tympanicum forms a still blunter angle than in R. esculenta. The 

 back branch of the tympanicum is still shorter than in R. esculenta, 

 so that the straight line connecting the articulations of the two jaws 

 invariably crosses the condylus. The plate of the inner branch of 

 the tympanicum is always shorter than in R. esculenta. 



The intermaxillary's (fig. 3) inner border never sinks so deep as 

 it does in R. esculenta. 



The vomerine teeth lie between the choana in two small, semi- 

 circular groups inclining towards each other at a very slight angle; 

 the group of teeth are always separated by a larger space than is the 

 case with R. esculenta in which the inner edges of the teeth groups 

 sometimes almost meet and never attain the straight line con- 

 necting the posterior border of the choance. 



The palatines differ from those of R. esculenta in as much as they 

 bear on their exterior side a rough, prominent bony crest. 



Median branch of os parabasale is in general narrower and more 

 rounded than in R. esculenta. Foramen occipitale magnum in old 

 individuals, oval, in very young ones, round. 



If we survey (fig. 4) the skull from the back joining the tympani- 

 cum's two posterior corners by a line, it will just about cut 

 across the middle of foramen magnum. In R. esculenta in 90 per 

 cent of the cases this line touches the upper border of the foramen 

 magnum; with R. ridibunda the mentioned line invariably crosses 

 the upper third of the foramen magnum. 



The vertebral column (excepting the length of the urostylus) is 

 as long as the skull. Characteristic differences are to be found on 

 the second, third and eighth vertebrae. Whilst, with R. esculenta 

 the diapophysis of second vertebra presents a cylindric shape 

 (fig. 5), with only a few unimportant protuberances towards the 

 center of the front border, the diapophysis of second vertebra 

 of R. chinensis is flat and presents a well developed bony crest on its 

 anterior border (fig. 6). This bony crest is to be found in R. 

 ridibunda also. The outer half of the diapophysis of the third 

 vertebra is carved out, shovel-like (fig. 7). On the median side of 

 its posterior edge a projecting bone ridge extends to the base of the 

 diapophysis. This bone ridge is to be found neither in R. escu- 

 lenta nor in R. ridibunda. 



