304 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
including the species which I am able to describe from my own observations, thus 
making the accounts full on all points important for classification; the second, 
species which I have not myself seen. Of these latter T have compiled descriptions 
from other authors and have copied the best figures I could find. 
The species which are described from my own observations number twenty-nine, 
including all that have been found in America as well as a number of others. The 
remaining well-established species number seven. 
Finally, T have added a list and notes on doubtful species, species that are 
insufficiently described for recognition, and animals that have been wrongly classi- 
fied with the llattididcB. These are in many cases accompanied by copies of the 
original figures. 
Family RA'ITULIDT. 
Loricate rotifers, with the structure somewhat unsymmetrical in certain features. Lorica 
usually cylindrical and curved, or ovate or ovoid; closed all around, with an opening at each end 
for the protrusion of the head and the foot. The anterior portion of the lorica usually set off from 
the remainder as a liead-sheath, by a slight constriction. On the dorsal surface of the lorica, 
usually if not always somewhat to the right of the median line, a longitudinal area which is trans- 
versely striated; this striated area is generally oblique, and may be developed as a single or double 
ridge, a furrow, or remain smooth. ( It is absent in only two or three species. ) Eye single, occipital, 
attached to the brain. Foot short, frequently attached unsymmetrically to the lorica. Toes 
bristle-like, their place of attachment usually twisted so as to bring the right toe somewhat to the 
dorsal side of the left; the toes sometimes equal, but the right or dorsal toe usually shorter; some- 
times quite rudimentary. Minute, bristle-like ‘‘substyles” at the base of the toes. Trophi 
usually unsymmetrical , the right manubrium smaller than the left: sometimes rudimentary. 
Mucus glands and reservoirs much developed. 
Key to the genera and species. 
A. The two toes equal or the shorter toe more than one-third length of longer I. Diurklla Bory de St. Vincent. 
B. A single long toe with usually or always an inconspicuous shorter one, the latter not more than one- 
third the length of the longer one II. Rattulus Lamarck. 
I. DIURELLA Bory de St. Vincent. 
al. Toes equal. 
bl. With a single tooth at the dorsal or dorso-dextral anterior margin of the lorica. 
cl. The toes about one-third as long as the body; body elongated, cylindrical, curved 1. D. tigris Miiller. 
ct. Toes shorter, less than one-third the body length; body shorter and very small; no visible ridge. 
4 D. intermedia Stenroos. 
(See also 9. D. sulcata Jennings.) 
b2. No tooth (or tooth very inconspicuous, hardly noticeable) at the anterior dorsal margin of the lorica. 
cl. Foot minute, usually retracted within the lorica; toes very short: lorica ending behind in a sharp 
angle; two deep grooves surrounding the body nearits middle 9. D. sulcata Jennings. 
c2. Very small; lorica much swollen and rounded behind and above, bringing the foot entirely on the 
ventral surface. Otherwise much as in the last 10. D. cavia Gosse. 
cS. Body projecting much above and behind the foot; the toes wide apart at base, about one-third the 
length of the body 13. D. sejunctipes Gosse. 
c4. Body projecting behind and above the small foot; a ring-like fold or collar surrounding the lorica in 
front of its middle; toes slender, a'bout half as long as the lorica___ 14. D. collaris Rousselet. 
(See also 17. D. brevidacti/la Daday.) 
a2. Toes unequal (the right one shorter). 
bl. A single tooth at the anterior dorsal margin. 
cl. Body elongated, cylindrical, curved; the right toe about half as long as the left, or a little less than 
half 2. D. tenuior Gosse. 
c2. The body short, thick, curved, with a very prominent ridge; toes short, the right one a very littlfe 
shorter than the left 3. D. iveberi, n. sp. 
(See also D. uncinata Voigt, page 319, note.) 
