548 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 
MONOBOTHRIUM TBREBRANS Sp. ROY. 
[Plates 63, 64, 65; Figs. 1 to 21.] 
Body elongated, somewhat flattened, linear, slightly enlarged at the 
extremities, which terminate in blunt points, opaque, white. Head va- 
riable, subsagittate, wedge-shape or bluntly rounded, a little broader 
and thicker than the body, somewhat depressed dorso-ventrally but 
without distinct bothria, translucent white with more delicate cuticle 
than body. Posterior end of the body with irregular prominences 
due to the development of ova in the uterus. Genital aperture ventral 
about the posterior fifth; testes in front of genital aperture occupy- 
ing the greater part of the body; female genitalia behind the genital 
aperture. Largest specimen 28 mm. in length. Sometimes several 
with heads buried in common pit in mucous membrane of host. 
Habitat: Intestine of Catostomus ardens, Heart Lake, Wyoming, July 
28, 1890. 
Diesing makes this genus the type of his family Monobothria. 'The 
genera included are Caryophyltleus Gmelin, Monobothrium Diesing, and. 
Diporus Diesing. These cestods are peculiar in that the body is not 
segmented and contains but one set of genitalia. In other words a 
single individual corresponds to one proglottis of an ordinary tape- 
worm. The members of the group thus serve, in a measure, to connect 
the cestods and trematods. 
Several large suckers which had been taken in a trammel net were 
examined and about a dozen specimens of this parasite were obtained | 
from two of the fish. They were associated with Hehinoriy ynchus. tuber- 
osus, and in each instance several of the individuals were found to be 
attached to the intestinal wall with their heads buried in a common pit 
in the mucous membrane. Some of these clusters were preserved 
entire with a portion of the intestine. Upon examining the alcoholic 
specimens one was found 7 mm. in length, which was wholly inclosed in 
a pit in the mucous membrane. The walls of the pit were thick and— 
gristly and the head end of the parasite had nearly perforated the 
intestinal wall. 
The longest living specimen measured 28 mm.; as an alcoholic speci- 
men it measured nearly the same, presenting the following dimensions 
in millimeters : : Length, 27; breadth, median, 2, expanding near anterior 
end to 2.5, and near the posterior oad tapering rather abruptly to 1; 
thickness about 1, but increasing to 1.5 at the posterior end where there 
are two or three ricdeteene swollen or nodular places. 
The following observations are based on alcoholic specimens: A 
small specimen measured 17 mm. in length; median breadth, 25 mm.; 
breadth near extremities,2mm. The anterior end of this specimen was 
sagittate and thicker than the body, posterior end bluntly tapering, 
thicker than body, and somewhat swollen or nodular. Each end of the 
