24 PROCEEDINGS OF THE ACADEMY OF [1883. 



larger larvae of the present collection , approaches nearest that of 

 the Aniblystoma tenebroswni. These animals were abundant in the 

 small stream I examined, and swam with great rapidity, darting 

 about and hiding themselves among the fallen leaves that covered 

 the bottom. 



I. Processes with two rows of rami : 

 Rami with many thread-like fimbriae ; Siren. 



II. Processes with one — an outer — row of rami ; 

 processes horizontal. 

 A rudimental inner row of rami ; fimbriae thread-like ; Proteus. 

 III. No principal rami ; 

 A. Processes compressed ; fimbriae dependent from 

 lower edge ; 

 Fimbriae thread-like, extending on both outer and inner face of 

 process ; Necturua. 



Fimbriae flat, long, chiefly confined to the lower margin of process ; 

 Larvae of Spelerpes ruber; S. Mlineatus, and Gyrinophilus 

 porphyriticus. 

 Fimbriae few, subclavate ; Plethodon cinereus. 



A A. Processes long, narrow ; bearing fimbriae only 

 on the side next the body ; 

 Fimbriae simple, fiat, sub-equal ; Amblystoma. 



AAA. No processes nor rami ; fimbriae on the vertical 

 septa. 

 Fimbriae in numerous rows on the edge of the septa; slender, 

 unbranched ; Larva of Amblystoma tenebrosum. 



AAAA. Processes vertical septa, with rami on the 

 anterior edge ; 

 Rami bearing flat, thread-like fimbriae, which arise from the pro- 

 cesses posteriori}' and are often divided. Larva from Simiah- 

 moo, Washington Terr. 



Plethodon ieoanus sp. nov. 



This salamander resembles the Plethodon glulinosvs in various 

 respects, especially in coloration. It has, however, a compi'essed 

 tail like the P. intermedius, and short series of vomerine teeth. 



The vomerine series are straight, and do not quite meet on the 

 middle line. They are entirely behind the nares, and do not extend 

 exterior to them. The parasphenoid patches are united into one, 

 and are well separated from the vomerines. 



Form rather stout, and the tail short, equaling (from vent) the 



