342 PROCEEDINGS OF THE NATIONAL MUSEUM vol. lu 



(Virginia and Missouri records).— Rioja, 1943, Anal. Inst. Biol. (Mexico), 

 vol. 14, p. 544 (Mexican records). 



Type specimens. — Present whereabouts unknown. Originally from 

 crayfish — ^probably Cambarus bartonii — ^collected by Joseph Leidy in 

 streams in and around Philadelphia, Pennsylvania. Topotypes 

 (PCH 695) from Wissahickon Creek in Philadelphia have been studied. 



DiAGXOsis.- — A medium to large-sized, variable species of the Phila- 

 delphica group, characterized by the following combination of char- 

 acters (only well-preserved specimens, in series, can be determined 

 with certainty) : Peristomium divided into dorsal and ventral halves, 

 the dorsal larger and with four low marginal lobations; jaws relatively 

 large and subrectangular in lateral aspect, the dorsal jaw usually a 

 little larger than the ventral; male reproductive system moderate in 

 size, filling from half to two-thirds of the coelom of one side of segment 

 VI ; bursa elongate, at least twice as long as broad, the penial sheath 

 merging gradually into a fairly short ejaculatory duct; spermiducal 

 gland slender and recurved ventrad, twice the diameter of prostate, 

 latter long and slender, reaching to ental end of spermiducal gland. 



Description (from "typical" northeastern specimens). — Body 

 moderate to large in size, maximum length 5.0 mm. Proportions 

 about normal for the genus, but anterior part of body less attenuated 

 than in most species; segments iv to viii of about equal diameter; 

 prosomites about three times length of metasomites and of greater 

 diameter, at least on anteriormost segments; caudal sucker small, 

 its diameter less than that of segment i. 



Head fairly large, as long as first three body segments, and its 

 diameter equal to that of segment ii; largest basally, narrowing 

 slightly to base of peristomium which is set off by a distinct constric- 

 tion and divided into two subequal halves. Dorsal half somewhat 

 larger and longer than the ventral, and provided along its margin 

 with four low rounded lobes (not visible in poorly preserved specimens, 

 either macerated or shrunken), the ventral half with a median incision 

 dividing it into two broad lobes. Peristomium not or but very 

 slightly flared, generally continuing the head profile in lateral aspect. 



Jaws massive, anisomorphic, heterodont, the dental formula 5-4 

 or 3-4, sometimes 3-2 in old specimens; dorsal jaw slightly larger 

 than ventral, both, in lateral aspect, almost as high as long and thus 

 subrectangular in appearance. Median tooth of dorsal jaw and 

 paramedians of ventral larger than the lateral cusps but not to the 

 extent seen in such species asfallax, chirocephala, and others. 



Male reproductive system variable in size, usually occupying 

 from one-half to two-thirds of the coelom of one side of the segment. 

 Bursa typically elongate, at least twice as long as wide, most of the 

 length being contributed by the atrium; penial sheath of normal 



