OF WASHINGTON. 225 



tubercles appear to furnish characters of systematic utility greater 

 than the denticules beyond the tooth, which in nearly all cases 

 decrease in size distad so gradually that their number is a matter 

 of uncertainty, and appears subject to considerable variation. 



The identification of immature specimens is likely to be always 

 a matter of difficulty, especially if unaccompanied by adult ma 

 terial. Very young individuals have the forceps slender, equal, 

 and almost or quite without armature, which, with the asym 

 metry and other peculiarities of the adult, is acquired gradually. 



Left arm of forceps without tubercles ; tooth located far below the mid 

 dle; denticules few (4-5) and small, but arranged in two rows: J. athe- 

 narum, sp. n., Athens, Berlin Museum. (Plate I, figs. la-ib.) 



Left arm with few to many (3-20) tubercles usually arranged in two 

 rows; tooth in nearly all cases located at or near the middle; denticules 

 in a single row 



Right arm with a single continuous row of about twenty small teeth, 

 none of which is conspicuously larger or more prominent than the others : 

 y. hubbardi, sp. >/., Chiricahua Mountains, Arizona, U. S. Nat. Museum. 

 (Plate I, figs. 2a-2b.) 



Both arms of forceps with one or two conspicuous teeth or nodiform 

 prominences 



Right arm with a large, smooth and even sinus below the tooth, then 

 with an abruptly prominent nodiform process or second tooth which fre 

 quently shows signs of being composed of three coalesced tubercles; su 

 perior row of one or two small, though distinct, tubercles: J. bidcns, sp. 

 ., Alabama, U. S. Nat. Museum. (PI. I, figs. 3a~3b.) 



Right arm with the sinus which separates the tooth from the first tuber 

 cle of the inferior row inconspicuous, or at least not as broad as the base 

 of the tooth; without a conspicuous abrupt process formed of coalesced 

 tubercles ; superior row various.. 



Right arm of forceps with four or five distinct, subequal tubercles in the 

 inferior row; superior row wanting; left arm distinctly narrower and 

 straighter, remaining nearly as narrow for some distance below the tooth 

 as for some distance above it; the proximal sinus beset with about 20 dis 

 tinct, spaced tubercles arranged in two subequal rows; tubercles not de 

 creasing in size proximad : Japyx multideiis, sp. ., Alabama, U. S. Nat. 

 Museum. (PL T, figs. 4a~4b.) 



Right arm with one or two tubercles, or the tubercles in two rows; 

 superior row represented by at least one distinct tubercle; left arm not 

 conspicuously straighter than the right, if narrower than the right it is 

 distinctly broader immediately below the tooth than above it; tubercles 

 less distinct, less numerous, and decreasing in size proximad 



Right arm of forceps in adult specimens with the proximal edge of the 



