100 Records of the Indian Museum. [Vol. XV. 



The tympanic cavity is lined all alonj^ by mucous membrane which 

 is very vascular and pigmented. 



The annulus tympanicus (figs. 4, 5, A. T.) is a cartilaginous frame- 

 work of the shape of a short truncated cone, broad outwards and nar- 

 rowing towards the inner side. The frame is not a complete structure, 

 but is interrupted on the dorsal surface, the space between the two 

 parts being occupied by a cartilaginous process («', Parker's swpra- 

 stapedial) of the extrastapedial cartilage of the columella auris. The 

 annulus tympanicus is supported on the anterior, dorsal and ventral 

 surfaces by the squamosal bone, while posteriorly by muscles. The 

 columella auris (fig. 6) has the oval outer surface of the extrastapedial 

 cartilaginous portion (a) embedded in the tympanic membrane {text 

 fig. 2), wdiilst the suprastapedial processes [a') from its posterior surface 



A.T- 



■^Kf^A^-^ 



-fjxy. 



T. '^^' 



P^' 



// 





^^m ■% ¥te^»'* 



Fig. 2. — Transverse section of the ear of R. tigrina through the region of the cohimella. 



goes to complete the annulus tympanicus as has been described above. 

 The middle bony portion or the mediostapedial {h) after passing through 

 the tympanic recess continues through the deeper portion of the tympanic 

 cavity, to end in the cartilaginous interstapedial (c), which fits into the 

 fenestra ovalis (fig. 4, /. o.). 



Having described in detail the structure in R. tigrma, I will now 

 describe the condition of the tympanic area of some other Indian frogs. 



FiRMISTERNIA. 



Family Eanidae. — 



Oxyglossus. — According to Boulenger (3) the tympanum ^ is indis- 

 tinct in this genus. Tn specimens of 0. lima and 0. Icevis the tym- 

 panic area is not distinctly marked off, but the attachment of the colu- 



^ The word tpnijinvmn used here and further on is used in the sense in which it is 

 used by Boulenger and is equal to lytvpanic area of the suggested nomenclature. 



