26 Proceedings of the Royal Physical Society. 
it does not appear to be so, and other characters concur with 
this to establish the species. 
This one is certainly not well named ; as, though un- 
doubtedly a small animal, it is the largest of the North Ame- 
rican species. 
Soreos Forsteri, Rich. — The tail in this species is quad- 
rangular. It is the smallest quadruped known to the Indians ; 
and I cannot call to mind any quadruped with which I am 
acquainted, from any quarter of the world, which is smaller. 
Among the specimens which have been sent me is one 
which differs slightly from the description of S. Forsteri. 
Its colour is wholly mouse-dun, whereas that of Forsteri is 
v/holly clove-brown on the back. The specimen is in spirits, 
however ; and the clove-brown being, from what we see in 
other specimens, a tinge of that colour in certain lights, it is 
probable that the darker colour is merely owing to the medium 
in which it has been sent ; at all events, that the specimen is 
at most only a variety. 
American Otter {Lutra Canadensis). — I have received a 
specimen from the York Factory district, in the shape of a 
medicine-bag, which is a favourite use of it with the na- 
tives. 
II. On New Protozoa. — (1.) Lagotia producta. (2.) Zooteire areligata. 
(3.) Corethria Sertulariae. (4.) On Stentor Mulleri and Stentor 
castaneus. By T. Strethill Wright, M.D. 
Description of Plate II. 
Fig. 1. Lagotia producta, group enlarged. 
2. Single specimen of do. 
3. Diagram showing section of tube — a, chitinous ribbon — h and c, in- 
ternal and external fleshy coats. 
4. 5, 6. Young of L. producta in various stages, 
7. Zooteirea religata — a, extended — h, contracted. 
8. Corethria Sertularice—a, "cushion" — &, "mop" — c, Gregarina-like ap- 
pendage. 9. Summit of "mop" — «, external, and 6, internal coat. 
10. Summit of Gregarina-like appendage. 
11. Salpistes Mulleri, — a, gelatinous lorica. 
1. Lagotia producta. (Figs. 1—6.) 
At our meeting of the 22d April 1857, I described Lagotia 
