166 TAPE WOK MS OF HARES AND RABBITS STILES. VOL.XIX. 



Bureau of Animal Industry by Professor Elrod, of Bloomington, Illi- 

 nois, with the following label : " From Mesenteries of Canada Porcupine. 

 Snake River, 1 near Nat. Park, Aug., 1894, M. J. Elrod." 



The following specific description will easily allow the recognition of 

 the form : 



Diagnosis. Bertia americana (Stiles, 1895), Stiles, 1896: Strobila 

 attains 33 mm. in length by 6 mm. in breadth and contains about 90 

 segments, the oldest of which are 0.8 mm. long. In some specimens 

 the posterior segments become much narrower, longer, and thicker than 

 the middle segments. Head, unarmed, measures 0.6 mm. broad by 0.38 

 mm. long by 0.32 mm. thick, and is nearly rectangular in apex view. 

 The neck is absent, and the head is frequently retracted into the body, 

 as in Drepanidotcenia laceolata. Suckers round, 0.176 mm. in diameter, 

 open anteriorly. Genital anlagen visible in the earliest segments. 

 Genital pores alternate in posterior half of margin. Male organs: Tes- 

 ticles form a continuous band in the distal portion of the median field, 

 extending on both sides to the longitudinal canals; about seventy testi- 

 cles to a segment; vas deferens runs in the proximal portion of the 

 segment; cirrus-pouch lies dorsal of the vagina, is very muscular, 0.48 

 mm. long by 0.144 mm. broad and extends to the ventral canal ; it con- 

 tains a vesicula semiualis (0.19 mm. long) in its proximal portion, and 

 the rather short, retracted, spinous cirrus in its distal portion. Female 

 organs: The anlagen of the glands are seen immediately back of the 

 head in or near the median line ventral of the testicles ; at first the 

 glands are but little differentiated, but on their pore side a globular 

 receptaculum seminis rapidly develops and becomes filled with sperma- 

 tozoa; the glands develop rapidly, coming to lie right and left of the 

 median line, the ovary becoming quite broad. The development of the 

 uterus could not be followed in detail, but eventually it occupies the 

 entire median field and becomes filled with ova 40 n in diameter; bulb 

 of pyriform body 16 to 18//. Excretory and nervous systems: 2 Dorsal 

 canals lie lateral of ventral canals and possess a thin lining. Genital 

 canals cross the longitudinal canals and nerves dorsally. Calcareous 

 corpuscles absent. 



Hosts. Yellow-haired Porcupine (Erethizon epixanihus], by Elrod; 

 Canada Porcupine (E. dorsatus), by A. K. Fisher. 3 



1 The Canada Porcupine (Erethizon dorsatm) does not extend so far west ; the host 

 must have been the yellow-haired Porcupine (E. epixanthus). 



2 The excretory system of this form will repay a careful study; in several anterior 

 segments (transverse sections) I found the dorsal canals connected with the trans- 

 verse canals, see pi. x, fig. 8. 



Since finishing this paper I have found some specimens in the Bureau of Animal 

 Industry collection (No. 1502) which agree with Elrod's specimens, and bear the 

 label, "E. dorsatm." These specimens were collected by Dr. A. K. Fisher at Lake 

 George, New York. Fisher states that nearly every porcupine he has examined har- 

 bors this worm. 



Cobbold, in 1862, examined some parasites from the same host-species and deter- 

 mined them as "Tcenia pectin ata," with pores "all on one side." 



