334 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
History. — This seems to luive been the first of the Rattulidce observed. It was discovered by 
Eichliorn in 1775 and was called by him the Water-Rat (“die Wasser-Ratte Muller in 1776 
gave it the name Trichoda rattus. Muller, Lamarck. Bory de St. Vincent, Dujardin, and various 
others have considered this species to be identical with R. carinatus Lamarck. This view has 
some evidence in its favor, though it can not be considered established. If it should ever be 
shown conclusively that the two are only forms of the same species, the name Rattulus rattus 
would prevail over R. carinatus as being the older name. 
Descriptions or figures of this species are to be found in Elirenberg (1838), Perty (1852), 
Eyferth (1885), Tessin (1886), Plate (1886), Hudson & Gosse (1889), Levander (1894), Scorikow 
(1896). Stenroos (1898). 
Distribution.- In America this species is very common amid vegetation in quiet waters. I 
have found it in the following localities: Put-in Bay Harbor, Lake Erie; Long Point, Canada, near 
“ the Cottages, - ’ on the north shore of Lake Erie; pools and swamps on South Bass Island in Lake 
Erie. It has been recorded by other observers in the United States as follows: New York (Ehren- 
berg, 1843); near Minneapolis, Minn. (“J. W.,” 1883); near Cincinnati, Ohio (Turner, 1892); 
Sandusky Bay, Lake Erie (Kellicott, 1897). 
In Europe: England (Gosse, 1889) ; Ireland (Glasscott, 1893: Hood, 1894) ; Germany (Bartsch, 
1870; Plate, 1886: Tessin. 1886); Tyrol (Dalla Torre, 1889); Bohemia (Petr. 1890); Finland 
(Levander, 1894; Stenroos, 1898); Switzerland (Ternetz. 1892); Hungary (Toth, 1861; Bartsch, 
1877; Kertesz, 1894; Daday, 1897); Livland, Russia (Eichwald. 1847); near Kharkow, Russia 
(Scorikow, 1896); also in Ceylon (Daday, 1898); abundant in Greenland (Bergendal, 1892). 
29. Rattulus lophoessus Gosse (pi. xi, figs. 98, 99). 
Sy non ym : Mastigocerca lophoessa Gosse ( 1889 ) . 
Distinguishing characters . — The distinctive features of this animal are the long, high ridge, 
reaching from the anterior end to the very foot and inclined far over to the right; the fusiform 
body, the unarmed anterior margin of the lorica, and the short rudimentary right toe, one-fourth 
the length of the main toe. It closely resembles R. carinatus Lamarck in many respects, but 
differs from it in the length of the ridge and in the toes. 
External features . — The body is fusiform in shape, and somewhat more elongated than in 
R. carinatus Lamarck. The liead-slieath is marked off from the remainder of the lorica by an 
evident constriction. The anterior edge of the lorica is without teeth or spines; it has a shallow 
depression in the ventral middle region (fig. 98). 
The ridge is nearly as high as in R. carinatus and extends from the anterior edge of the lorica 
to the very foot. It is situated considerably to the right of the middle line and is inclined far over 
to the right, resembling thus the right one of the two ridges in R. bicristatus Gosse. It is striated, 
as in R. carinatus Lamarck, and the striations extend considerably to the left of the ridge, ending 
at a well-defined line (fig. 99). Gosse (1889) and Weber (1898) describe the ridge as being inter- 
rupted, so as to form two or more arches. This was not the case in the specimens which I studied 
nor in those described by Bilfinger ( 1 894) . 
Corona . — The corona has the usual dorsal club-shaped process, according to Bilfinger (1894); 
it lias not been studied otherwise. In the preserved specimens at my disposal the corona was 
partly withdrawn. 
Antennae. — The dorsal antenna is situated considerably to the left of the ridge at the edge of 
the striated area. The lateral antennae I have not been able to see in the preserved specimens. 
The right one is figured by Bilfinger (1894) in the usual position on the posterior third of the body. 
Foot . — The foot is a short cone, of the usual character. The lorica projects far back over its 
base on the left side (fig. 99). so that the foot is free to bend to the right, but not to the left. 
Toes (fig. 98).— The left or main toe (/. t.. fig. 98) forms a long, nearly straight rod. about two- 
thirds as long as the body, Above its base, separated from it by a well-marked gap. is the right 
toe (r. t. ) . about one-fourth to one-third as long as the main toe. The right toe is bent toward 
the main toe, its tip overlying the latter. At the base of both the main toe and the smaller one are 
one or two scale-like substyles. The larger lobe of the mucus reservoir (in. r.) opens at the base 
of the main toe; the smaller lobe at the base of the rudimentary right toe. 
