NO. 2037. NORTH AMERICAN SPRING-TAILS— FOLSOM. 465 



As Schaffer remarks, the postembryonal changes are so great that 

 one knowing only the smallest and the largest individuals might 

 easily mistake them for two distinct species. 



In the largest specimens the unguis sometimes shows a trace of a 

 seventh tooth at the distal end of the series. The tooth of the 

 unguiculus may or may not be present, but usually occurs on large, 

 well-preserved specimens. The total number of dental spines 

 increases with age and varies slightly in individuals of the same size. 

 Agren gives the formula for European specimens as 4-6, 1/3, 1, 2, 1. 

 This would apply also to most American specimens, though a more 

 representative formula is 4-6, 1/2-5, 1, 2, 1. Rarely the formulae 

 7, 1/5, 1, 2, 1 and 4, 1/2, 1, 3, 1 occur. 



Linnaniemi ('12, p. 179) gives as the extreme formula for the dental 

 spines 5-7, 1/1-2, 3, 1-3, 1-2, 1. I have never seen, however, large 

 spines at the base of the second series. Regarding the spines as 

 forming two series, separated by the transverse suture, new spines 

 appear at the base of each series, and these spines are small. In the 

 number of spines the dentes of the two sides seldom differ by more 

 than one. 



The number of intermediate teeth on each mucro is rarely eight 

 to eleven. 



Reuter ('91, p. 228) gave the name of sibiricus to a variety of 

 vulgaris, characterized by its yellow body color and twelve dental 

 spines — five proxunal and seven distal. Linnaniemi ('07, '09, '12) 

 regards sibiricus as a distinct species, and has described it fully 

 ('12, p. 180) as sibiricus (Reuter) Axelson. His material is certainly 

 not vulgaris, since the dental spines have the formula 1-3, 2/3-5, 2-3, 

 and their maximum number is only thirteen, even in specimens 

 4 mm. in length. 



There is, however, a clear yellow variety of vulgaris, of which I 

 have specimens from Germany (from Schaffer) and from Maine, Mas- 

 sachusetts, and Colorado, along with gradations between the yellow 

 variety and a hea\T.ly pigmented form. 



Synonymy. — T. vulgaris is a common species in Europe, where 

 there has been no question as to the vahdity of the name vulgaris, 

 TuUberg's description and figures being sufficient to define the species. 



My American specimens agree with the European examples that I 

 have received from Schaffer. 



Some of the specimens referred to T. plumbeus Linn^us by Packard 

 ('73, p. 38) are T. vulgaris, as I found by an examination of his speci- 

 mens in the Museum of Comparative Zoology at Cambridge. Thus 

 one of the five specimens labeled ''Brunswick, Me., Sept. 10, A. S. P." 

 is vulgaris, and six of the twelve labeled "Salem, Mass., A. S. P." 

 are vulgaris. 



95278°— Proc.N.M.vol.46— 13 30 



