20 G-H Canadian Arctic Expedition, 1913-18 



filling up the whole of the proglottis anteroposteriorly below the cirrus-sac; 

 0-29 to 0-34 mm. in length by 0-070 to 0-072 in diameter. Ovary somewhat 

 bilobed and lobulated, 0-135 to 0-32 mm. in width by 0-045 to 0-065 in length 

 by • 35 in depth Vitielline gland ellipsoidal, median, posterior to ovary, 50 to 

 60ju in diameter. Uterus when first apparent in toto preparations occupies the 

 middle third of the proglottis transversely, when gravid extends well beyond 

 the excretory vessels which appear in transections nearly surrounded by the 

 organ on account of its being somewhat lobulated dorsoventrally. The receptac- 

 ulum seminis hkewise appears imbedded in the dorsal side of the poral half of 

 the uterus. Length of uterus, 0-12 to 0-15 mm., width, 0-75 to 1-00, depth, 

 0-12 to 0-28 (these differences due to the lobulation). 



Eggs spherical; outer envelope, 56ju in average diameter, middle, 37/j, 

 oncosphere, 26 to 30/i. 



Habitat. — Stomach of Passerella iliaca (Merrem), the fox sparrow, in com- 

 pany with Choanotaenia passerellae Cooper, sp. nov.; Teller, Alaska, August 3, 

 1913. 



To this species I refer six strips of proglottides without scolices, two of them 

 evidently belonging to the same worm, having a combined length of 56 mm. and 

 maximum breadth of 1 - 2 mm. Their anatomy agrees with the brief description 

 given by Skrjabin, excepting only for the facts that the antiporal borders of the 

 testes do not extend to the antiporal excretory vessels and the ovaries are much 

 narrower— 0-135 to 0-165 mm. rather than 0-29 to 0-32 ("with a width of 

 proglottis of 1-02 mm.") of Skrjabin. 



Skrjabin's description is slightly amended to include the latter data, while 

 other specific characteristics are here given for the sake of a clearer definition of 

 this, one of the largest of the species of Aploparaksis. 



Aploparaksis sp. 



To this genus I also refer a lot of small and poorly preserved cestodes taken 

 from the posterior portion of the intestine of a specimen of Somateria v-nigra 

 Gray at Bernard hafbour on June 27, 1916, at C.A.E. Station 49r. The lot con- 

 sists of portions of at least two worms, much coiled, without scolices and in such 

 a poor state of preservation that I was unable to ascertain to what species they 

 belong. 



However, they resemble A. birulai Linstow (1905:8), so far as I know the 

 only species of Aploparaksis which has up to date been found in a species of 

 Somateria, in the following points: The length is approximately the same (27-5 

 mm. vs. 24-8 mm. ior A.h.); the longitudinal muscles are disposed in two layers, 

 an outer among the subcuticular cells and an inner and much stronger in the 

 usual position; there are no calcareous bodies; the geinital pore is unilateral 

 and opens in the middle of the lateral border of the segment; the testis is 

 spherical in shape and its diameter is about one-tenth of that of the segment; 

 the cirrus-sac is one-third the diameter of the proglottis in length, namely, 0-16 

 mm. (by 36;u in diameter); the cirrus is cylindrical and heavily armed; the 

 vagina is situated ventral to the cirrus-sac ; the receptaculum seminis, 37 to 50m 

 in diameter, is ventral to the ovary; and finally the eggs are 37/i (the embryo 

 25ju) in diameter — 40 by 34yu in A.h. On the other hand they differ from A. 

 birulai in that the lengths of the proglottides are anteriorly, 54/i (vs. 12ju), 

 posteriorly, 60/i (19^) and when ripe lOlju, while the respective widths are 0-24 

 mm. (0-13 mm.), 0-38 (0-57) and 0-48 (0-25); the cirrus is much larger, 0-145 

 by 0-015 mm. (0-023 by 0-0052); and the testis is more median in position. I 

 was able to determine neither the positions nor the courses of the excretory 

 vessels and the nerves. The lengths and widths of the ovary and uterus (when 

 filled with eggs) are, respectively, 0-054 and 0-127 mm., and 0-11 and 0-38 mm. 



