Trematodes and Cestodes 17 G-H 



but due to longitudinal contraction. Anterior segments infundibuliform but 

 much broader than long; middle, more nearly quadrate and about twice as 

 broad as long; posterior, less than twice as broad as long with convex lateral 

 borders, 1-40 mm. in length by 1-95 in breadth. 



Genital pore at the middle of the lateral border of the segment on a low 

 rounded papilla, 0-2 mm. in diameter by 0-08 in height and in many segments 

 retracted so that its summit is level with the edge of the proglottis. Opening of 

 vagina immediately ventral to that of cirrus at the bottom of a genital cloaca, 

 0-125 mm. in depth by 0-036 in diameter. 



Testes arranged in two or three layers posterior, lateral and somewhat 

 dorsal to the central glands and ducts of the female organs; 15 to 20 in number, 

 spheroidal in shape, 80 to 120^ in diameter. Proximal coils of vas deferens 

 median and near the anterior border of the segment, distal less compact coils 

 surrounded by numerous highly vacuolated glandular cells; no external seminal 

 vesicle. Cirrus-sac almost cylindrical in shape, short and stout, 0-24 mm. in 

 length by 0-07 to 0-09 in width. Cirrus very short and thick and armed with a 

 host of minute stout spinelets. 



Vagina thick-walled and muscular from genital cloaca to within the ventral 

 excretory vessel, about 0-11 mm. beyond which it turns abruptly dorsally then 

 medially to become the receptaculum semmis; laterally it courses directly 

 beneath the cirrus-sac but medially it diverges posteriorly. Seminal receptacle 

 ellipsoidal in shape, 0-15 mm. in length by 0-12 in diameter. Ovary median, 

 semiannular in shape, with the forwardly directed convexity bearing about ten 

 short, stout tubules; whole organ, 0-15 mm. in width by 0-09 in length. Shell- 

 gland inconspicuous. Vitelline gland median, spheroidal in shape, about 70/x, 

 in diameter. Uterus composed of a median short and slightly coiled canal, 

 leading to a main A-shaped stem, from which numerous saccular lobules invade 

 the parenchyma in all directions (Fig. 14). The lateral lobes enlarge before the 

 more median ones, and the whole organ eventually fills up the whole of the 

 medullary parenchyma. 



Eggs, measured in toto preparations cleared in oil of wintergreen, 0-125 to 

 0-145 mm. in diameter, oncospheres 55/i in diameter. 



Type host. Somateria v-nigra Gray, the Pacific eider, in the stomach, in 

 company with Aploparaksis sp. and Fimbriaria intermedia. 



Type locality. Bernard harbour, Northwest Territories, Canada; C.A.E. 

 Station 49r. 



Collected by Mr. Frits Johansen, June 27, 1916. 



The paratype is deposited in the Victoria Memorial Museum, Ottawa, 

 Canada, (Annelids, etc., Catalogue No. 83). 



This species obviously does not belong to Lateriporus teres which was 

 described by Krabbe (1869:284) and Fuhrmann (1907:521) from Somateria 

 mollissima, the European eider, from Greenland. It resembles, however, one 

 of the other four species of Lateriporus, namely L. biuterinus Fuhrmann (1908: 

 56), which was taken from a number of South and Central American 

 birds as well as from the European Oidemia fusca (L.), the velvet 

 scoter, a close relative of Somateria, in that the uterus is divided into 

 two parts at the median line and each of these is subdivided into a number 

 of lobules. But the lobulation is carried on to a much greater extent in L. geo- 

 graphicus, as indicated in figure 14, which represents three stages in the develop- 

 ment of the organ. Eventually the two main limbs come close together in the 

 median line posteriorly and the whole parenchyma, cortical as well as medullary, 

 becomes filled with the eggs. On the other hand, L. geographicus differs from 

 L. biuterinus in that there is no seminal vesicle just outside of (median to) the 

 cirrus-sac ; the vagina opens ventral to the cirrus instead of ahead ; the receptac- 

 ulum seminis, vitellme gland and ovary are much smaller; the ovary is differently 

 shaped and lobulated; and, finally, the oncospheres are much larger (55/z vs. 



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