234 A llonograjyh of Sci/ionotus. 



Dentate lamellse with four rounded teeth. 



Pectinate lamellse six. 



Mentum triangular-cordate, sub-equal in length and width, mod- 

 erately emarginate posteriorly, acute-angled anteriorly. 



Cardo large, nearly half as long as the mentum. 



Lingual lobes with few cones ; median lobe with styliform processes. 



First segment sub-elliptical, narrower than either the head or the 

 second segment. 



Anterior segments laterally curved forward, the posterior with the 

 corners produced caudad ; dorsal surface of all the segments densely 

 roughened with setiferous granulations more or less regularly arranged in 

 4-6 transverse rows. 



Lateral carinse nai'row, ^ as wide as the body cavity, thick, granular- 

 serrate, reduced or obsolete on segments 6-9 in females. 



Anterior sub-segments punctate. 



Supplementary margins finely pectinate. 



Kepugnatorial pores opening dorsally on smooth elevations near the 

 posterior corners of segments 5, 7, 9, 10, 12, 13, 15, 16, 17. 



Anal segment tuberculate, decurved, acuminate, truncate at apex, with 

 four setrt;. 



Anal valves with two setigerous tubercles, not placed on the raised 

 margin. 



Pre-anal scale seini-elliptic, with segiterous tubercle on each side. 



Legs of male much larger than those of female, some of them crassate 

 and specially modified for copulation ; second joint without spine ; joints 

 of normal legs in order of length : 6, 3, 2, 5, 4, 1 ; terminal joint inferiorly 

 tuberculate-serrate in male, the sub-tenninal inferiorly papillate. 



First pair of legs free, small and slender, the coxa longer than any 

 other joint except the last. 



Second pair of legs free in female ; of the same shape as the succeed- 

 ing ; coxa not specially modified. 



Genitalia of female sub-spherical, external, protrusible. 



Genitalia of male bi-hamate, the distal hamus articulated at base, beset 

 with fine laciniaj ; basal joint expanded to receive the distal. 



Segments of adult 19. 



DishHhution. — Northeastern North America, 



From Polydesmus this genus ditfers in having the dorsal sur- 

 face uniformly covered with small, setiferous granulations, 

 arranged in 4 to 6 rows; in having 19 less segments and no 

 pores on segments 18 and 19 ; the pores on rounded elevations. 



From Braeh\desmus it is distinct in the convex dorsum cov- 

 vei'ed with sub-equal squamae arranged in 4-6 transverse rows, 

 instead of having three rows, with the anterior squamae and those 

 of the carinse several times as large as the others. 



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