306 PROCEEDINGS OF THE ACADEMY OF 



of the Yellowstone River, to be mucli infested with a species of 

 tapeworm. A number of specimens of the worm, collected by 

 C. Carrington, have been submitted to his examination, but, un- 

 fortunately, most of them are so far decomposed as nearly to be 

 reduced to the condition of pulp. The worms are stated to have 

 been taken from the abdominal cavity, but not from the intestinal 

 canal, and often were found beneath the skin, extended among the 

 muscles or inclosed in OA^al sacs. Several cysts preserved entire 

 contained worms in a better condition for examination than the 

 others, and from these the characters of the parasite have been 

 ascertained. It belongs to the old genus Bothrioccphalus^ and 

 to that section now named Dibothrium. Two species of this 

 genus have long been known as infecting the salmon and other 

 members of the same genus of fishes in Europe, but the parasite 

 of the Yellowstone trout appears to be a different one. 



Two of the best preserved specimens measured five inches long 

 by a line wide at the broadest part. The head, about a fourth of 

 a line in diameter, is obcordate. The two suckers or bothria are 

 thick and discoidal, placed back to back, obcordate in outline, and 

 directed with their broad and slightly depressed surface towards 

 the margins of the body. The body is flat, thick, with rounded 

 margins, and is narrowly annulated or segmented. The annula- 

 tions due to muscular bands measure about ten to the line. Seg- 

 ments, independent of the annulations if existing, could not be 

 distinguished, perhaps on account of the badly-preserved condi- 

 tion of the specimens. No genital apertures are visible at the 

 sides nor at the margins. No internal organs are visible, but the 

 soft solid interior tissue is filled with round corpuscles resembling 

 starch granules. These are, however, composed of carbonate of 

 lime, as they are dissolved by acetic acid with an abundant evo- 

 lution of carbonic acid. 



From the form of the head, the worm was named Dibothrium 



CORDICEPS. 



Numerous leeches collected b}^ Prof. Ilayden's assistants, 

 Messrs. Carrington and Dawes, in a lake in Wyoming Territory, 

 appear to belong to the species Aulastomum lacustris, first dis- 

 covered several years ago in Twin Lake, Minnesota.* Mr. Car- 

 rington informs us that the head of a horse, which was thrown 

 into the lake, in a few hours appeared black from the quantity 

 of these leeches which adhered to it. It is barel}^ probable that 

 this leech is the one described b}^ Thomas Say, in Long's Ex- 

 peditions, under the name of Hirudo marmo7-ata, though the 

 characters do not accord with his description of the latter. It 

 is not improbable that the two are quite distinct. H. marmorata, 

 togetlier with another species, H. lateralis, was obtained from 

 small lakes on the high land between Lake Superior and Rainy 



» Proc. Acad. Nat. Sci., 1868, p. 229. 



[February 13, 



