ON THE ANATOMY OF RA^YA TIGIITXA. 603 



44. Some Notes upon the Anatomy of Rana tigrina. By 

 Geo. E. Nicholls, D.Sc, late Professor of Biology, 

 Agra College, India *. 



[Received October 9, 1915 : Read November 9, 1915.] 



(Text-figm^es 1-3.) 



In several skeletal and otlier characters, Rana tigrina — the 

 so-called Bull-frog of India — differs markedly from our common 

 European grass or water frogs [R. temporavia, R. esculenta). 

 Tiiese two frogs, which resemble one another fairly closely, 

 appear to be the only species of which a detailed description has 

 been given, and figures of one or the other alone appear in text- 

 books all the world over. For the Indian form these figures are 

 in some respects quite misleading, and since this frog is now 

 generally used thi-oughout India as a laboratory type, it has 

 seemed desirable that attention should be called to those features 

 in which R. tigrina differs from its European congeners. 



1. The Vertebral Column. 



In correspondence, doubtless, with the much larger size of this 

 frog, the vertebrae are distinctly more stoutly built than is the 

 case in R. temporaria. The neural arches are, relatively, greatly 

 developed antero-posteriorly. Thns, when viewed from above, 

 the vertebral column of this species does not show a series of gaps 

 between the arches such as is so clearly seen in R. temporaria 

 {cf. Howes, '03,_fig. 35). On the contra.ry, there is, in R. tigrina, 

 a very marked overlap of each arch dorsally npon that immediately 

 posterior to it, and accordingly, when the vertebrae are in position 

 (text-fig. 1), the centra are not visible from above. 



Such a condition as this is said to be imbricate, and to 

 characterize the Discoglossidte and Pelobatidaj (Boulenger, '97, 

 p. 38). Concerning the European species of Ranidse, Boulenger 

 points out that precisely the opposite condition prevails. His 

 statement may be quoted : — " The neural ai-ch is either closed 

 above ... or notched between the zygupophyses so as to expose 

 the spinal cord between every two vertebrae ; the latter type is 

 most marked in Rana, in which, the lateral openings for the exit 

 of the spinal nerves being also of large size, the vertebral column 

 forms an open-work above and on the sides." 



While this " open-work " vertelfi-al column is seen typically in 

 the European Ranidse, it is also found in most of the other 

 Anura, so that Boulenger notes this as one of the characters 

 which separate the Bufonidse and Hylidye from the more 

 generalized Arcifera. In this imbricate condition of the 



* Communicated b.v Prof. Arthue Desdy, D.Sc, F.R.S., F.Z.S. 



