16 PROCEEDINGS OF THE ACADEMY OF [Jan., 



following tentative key, of the genera Plethodon, Hemidactylium, 

 Desmognathus, Gijrinophilus, and Sjjelerpes follows, with the reserva- 

 tion that so far as known the first two do not have aquatic larvae. 



a. — Gills unpigmented, presenting a glistening white appearance; 



legs stout Desfnognathus fusca 



aa. — Gills pigmented; legs slim. 



h. — Dorsal surface lighter than sides. 

 c. — Dorsal surface immaculate save slight pigmentation 



along median line; a black lateral band 



Spelerpes longicaudus 

 cc. — Median dorsal surface immaculate; a lateral row of 



dark spots *S. bislineatus 



66.— Back and sides alike. 



d.— Head short = *S. ruber 



dd. — Head long Gyrinophilus porphyriticus 



D. fusca, length of largest larva, 44 mm. ; smallest adult 27 mm. 

 >S. longicaudics, " " " 42+ " " " 49.5 " 



S. bislineatus, " " " 70 " " " 47 " 



S. ruber, " " " 110 " " " 74 " 



G.porphyriticus, " " " 100+ " " " — " 



S. ruber and G. porphyriticus are seldom met with in the same locality. 

 The final color pattern of the plethodont salamanders is the result 

 of the gathering of pigment on the sides of three rows of unpigmented 

 spots. These spots vary with the species in number, size and date. 

 In D. fusca the dorsal series is quite large and the two series are 

 confluent at an early age and form the light dorsal area so charac- 

 teristic of the young of that species. In >S. longicaudus at 30 mm. 

 (smallest larva seen), the dorsal areas have merged along the back 

 and the pigment forms a definite lateral line. At this stage the 

 lateral spots are not noticeable. In S. bislineatus at the earliest 

 stage (17 mm.) the dorsal areas are very noticeable and the others 

 are not evident. Up to the age of about a year (30 mm.) the dorsal 

 areas retain their shape. As they break up, the lateral areas appear, 

 and these sometimes last after transformation. The dorsal areas 

 attract pigment which forms the lateral line at transformation. 

 Until transformation, however, this line is much broken and very 

 irregular more resemliling a chain than a band. This difference as a 

 chain and a band, connected with the lightness of the dorsal surface, 

 serves to differentiate between this species and S. longicaudus. 

 Furthermore, 8. longicaudus has a shorter development than S. 

 bislineatus, as it is a one-year instead of a two-year species. In 

 examples of the same size (30 to 40 mm.) the dorsal areas have 



