ROTATORIA OF THE UNITED STATES. 
305 
bn. With two teeth or spines at the dorsal or dorso-dextral anterior margin of the lorica. 
cl. The two teeth short, the right one larger than left; body long, slender, curved; right toe about half 
as long as the left, or less 5. D. insignis Herrick. 
c3. The two teeth short, the right one larger than the left; body short, thick; the foot turned beneath 
the ventral surface; the right toe a little shorter than the left 6. D. porcellus Gosse. 
cS. The two teeth developed into long, sharp, slender spines, nearly or quite equal in length; body long- 
conical in shape, scarcely curved; the two toes very close together and nearly equal (the left a 
little longer) 7. D. stylata Eyferth. 
63. With many (nine) teeth at the anterior margin of the lorica 8. D. rousseleti Voigt. 
64. Without teeth at the anterior margin of the lorica; foot at the posterior end of the body. 
cl. Toes very nearly equal 11. D. prachyura G-osse. 
c2. Right toe about two-thirds as long as the left 12. D. dixon-nuttalli , n. sp. 
(See also D. breviclaCtyla Daday, D. marina Daday, and D. helminthocles Gosse, which could not 
be taken into the key because certain important technical characters, particularly in regard to 
the anterior margin of the loi'ica, are unknown.) 
II. RATTULUS Lamarck. 
al. With a single tooth or projection at the anterior dorsal (or dorso-dextral) margin of the lorica. 
6 1. The single, not very conspicuous, tooth situated at dorso-dextral part of anterior margin of lorica, 
forming a prolongation of the ridge (the ridge may be inconspicuous) . 
cl. Body elongated, nearly cylindrical, not strongly curved; head-sheath sharply set off from the 
remainder of the lorica and very contractile; main toe about half the length of the lorica, accom- 
panied by a shorter toe one-third the length of the main one 18. R. gracilis Tessin. 
c2. Body elongated, nearly cylindrical, not strongly curved; the head-sheath not sharply set off nor 
very contractile; toe two-thirds the length of the lorica, or still longer 19. R. scipio Gosse. 
cS. Body elongated, nearly cylindrical, strongly curved 35. R. curvatus Levander. 
c4. Body elongated, fusiform, not strongly curved; anterior tooth very inconspicuous; toe one-half to 
two-thirds the length of the lorica; a small spur projecting backward from the base of the toe 
when the latter is turned forward 20. R. macerus Gosse. 
(See also R. unidens Stenroos (?) and R. cuspidatus Stenroos (?).) 
63. The single large tooth forming a triangular projection from the median dorsal part of the anterior 
margin of the lorica, overhanging the corona. 
cl. The lorica oval or ovoid in form 21. R. multicrinis Kellicott. 
c2. The lorica elongated, cylindrical. 
dl. The anterior tooth prolonged as a long, slender hook bending over the corona (but not always 
visible); toe almost or quite as long as the body 22. R. cylindricus Imhof . 
d2. The large anterior tooth forming a hood-like projection over the corona; body somewhat curved; 
toe about half the length of the body 23. R. capucinus Wierz. & Zach. 
(See also 36. R. dubius Lauterborn.) 
a2. With two long teeth or spines at the anterior margin of the lorica. 
bl. The two teeth at dorso-dextral margin of lorica; the right longer than the left 24. R. longiseta Schrank. 
63. The two teeth at the ventral margin of the lorica (?) R. roseus Stenroos. (?) 
a3. Without teeth at the anterior margin of the lorica. 
bl. Lorica with two prominent ridges on its dorsal (or dorso-dextral.) surface. 
cl. Very large; the two ridges very high and extending two-thirds length of body 25. R. bicristatus Gosse. 
c2. Smaller, the two ridges lower, reaching back only about half the length of body _ _ 26. R. mucosus Stokes. 
63. A single very prominent thin ridge on the dorso-dextral surface of the lorica. 
cl. The ridge high and thin, extending about one-half the length of the lorica 27. R. carinatus Lamarck. 
c2. The ridge high and thin, extending nearly or quite the entire length of the lorica 39. R. lophoessus Gosse. 
63. The ridge either not prominent or lacking (a low ridge can be detected in most of these species, on 
careful examination) . 
cl. Body broad, ovate, very unsymmetrical at the posterior end; no trace of ridge 30. R. latus Jennings. 
c2. Body short, thick, arched dorsally; toe longer than the lorica; lateral antennse protected by pro- 
jecting spines 31. R. bicuspes Pell. 
c3. Large; body long, slender, straight, tapering posteriorly; toe two-thirds the length of the lorica. 
32. R. elongatus Gosse. 
ch. Body short, irregular, somewhat conical; toe less than half the length of the lorica 33. R. stylatus Gosse. 
(See also R. brachydactylus Glasscott.) 
c5. Very small; body truncate in front, gently arched dorsally; toe about the length of the lorica; sub- 
styles very inconspicuous -34. R. pusillus Lauterborn. 
c6. Body oval, much larger than in the last; toe about the length of the lorica; substyles easily seen. 
28. R. rattus Muller. 
F. C. B. 1902—20 
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