64 ILLINOIS BIOLOGICAL MONOGRAPHS [352 



proglottis to proglottis. Shell-gland obscure. Uterus surrounded by glandu- 

 lar cells proximally; 0.2 5mni. in maximum diameter. 



Eggs, 36 by 24jLt in dimensions. 



Habitat: In the intestine of Pseudopleuronectes americanus (VValbaum), 

 the winter flounder, from Brandy Cove, St. CroLx River, at St. Andrews, New 

 Brunswick. 



Type specimen: No. 206.1 in the writer's collection. 



Co-type: No. 206.2 from the same, deposited in the collection of the Uni- 

 versity of Illinois. 



Since 1842, when Duvernoy described Bothrhnonus sturionis, the type 

 species and the only one reported for America up to date from a specimen of 

 Acipenser oxyrhynchus Mitchill { = A. sturio L.) collected by M. Lesueur in 

 1835, the following species have been found in Europe: Diplocotyle olrikii 

 Krabbe (1874), D. rudolphii Monticelli (1890:205), B.fallax Luhe (1900b:257), 

 B. nylandicus Schneider (1902a :72), D. cohaerens Linstow (1903:291) and B. 

 pachycephalus Linstow (1904:307). As pointed out by Schneider (1902:77), 

 D. serrata Linstow (1901:288) evidently does not belong to the genus at all. 

 But with none of these could the material studied in connection with the present 

 description be alligned. Altho it bears resemblances in individual points to 

 B. cohaerens and to B. pachycephalus, doubtless owing to the fact that these 

 have been better described than the others, including B. fallax, and closely 

 approaches B. nylandicus, yet it is so different from the latter that it is con- 

 sidered to constitute a new species. 



The scolex (Figs. 6-8,) is typical in that it is composed of two surficial and 

 almost hemispherical bothria arranged in the usual manner. These are well 

 separated not only posteriorly from the strobila but laterally from each other 

 by distinct grooves as in B. nylandicus. In all of the specimens studied the 

 apertures of the bothria, usually circular in shape and about 0.1mm. in diame- 

 ter altho in a few cases somewhat elongated dorsoventrally, were distinctly 

 separate. But since, as shown by Schneider, there is great variation in the 

 extent of fusion of the two apertures owing to differences in degree of contrac- 

 tion even in individual species, this separation is not considered to be of speci- 

 fic, let alone generic, value. The compressed lumen of the bothrium has a 

 transverse diameter of 0.3mm.; while the other measurements of the scolex 

 are as given in the table below. The short unsegmented region between the 

 scolex and the first set of genitalia, which has a length of about 1.5mm., may 

 be considered to be a neck. Excepting for the openings of the reproductive 

 organs and the protruded cirri, there are no external indications of segmenta- 

 tion. Internally this is also the case as regards the vitellaria and testes, which 

 are both strictly continuous from proglottis (set of genital organs) to proglot- 

 tis, as in the genus Bothriocephalus (vide infra). The strobila, which is quite 

 uniform in diameter from the region close behind the scolex, is about one-half 

 as thick as broad and sUghtly more convex ventrally than dorsally, as in B. 

 nylandicus. None of the specimens at hand were complete posteriorly. The 



