SOUND-TRANSMITTING APPARATUS OF CAUDATA 327 



lymphatic prominence which is placed in connection with the 

 supraclavicle by the jM. opercularis. More recently, the present 

 writer (Reed, '15) has interpreted certain aspects of the problem 

 bearing upon the morphology of the single fenestral plate in 

 Necturus and has pointed out that in its nature it differs from 

 the single element in both the Triton-Diemictylus group and 

 the Cryptobranchidae, although apparently agreeing with the 

 latter in skeletal connections, form, and general estate. A brief 

 review of these results will appear later in the present paper. 



For the present study there were available series of both larvae 

 and adults of most species considered, but some series were found 

 lacking in important stages. Of those which were chosen to 

 serve as type studies for a given taxonomic group an attempt 

 was made to obtain developmental stages as numerous and as 

 close together as possible. The results follow: Spelerpes bis- 

 lineatus, larvae 10, 15, 17, 19, 20, 21, 23, 25, 28, 31, 34, 37, 43, 

 and 55 mm., respectively; Desmognathus fusca, larvae of 10, 26, 

 27, and 30 mm.; Amphiuma means, embryos of 30 and 33 mm., 

 a mature larva and a newly transformed adult; Necturus em- 

 bryos of 11, 12, 15, 16, 17, 18, 19, and 20 mm. and larvae of 21, 

 22^ 23, 24, 25, 26, 35, 40, 43, 44, 48, and 70 mm. in length. 



THE PLETHODONTIDAE 



Spelerpes bislineatus was chosen as the type study for the 

 family Plethodontidae, chiefly because of the relative ease of 

 procuring material and partly because it was considered a gen- 

 eralized member of the family. As is usual in the Plethodontidae, 

 the ear capsule is fully ossified in the adult except the lips of the 

 fenestra and those points where connection is made with the 

 processes of the palatoquadrate. Both the fenestra and the fen- 

 estral plate are relatively elongate, but narrow in the vertical 

 diameter, as shown in figure 26. The stylus, a slender rod, is 

 attached to the cephalic portion of the plate and extends for- 

 ward and slightly upward where it joins the ventral edge of the 

 squamosum. In adults as large as 57 mm. there is no connec- 

 tion of stylus and os quadratum unless a very slender and 



