OF DENISON UNIVERSITY. 63 



Sp. 20. Metopidia dentata, sp. n. 

 [Plate I; Fig. 9.] 



In the shape of the lorica, this species resembles M. elliptica. 



Lorica smooth sub-elliptical, cephalad margin excavated. 

 From the bottom of the cephalad excavation of the ventral portion 

 of the lorica, a convex tongue projects half way to the cephalad ex- 

 tremity of the lorica. Caudad margin of the ventral valve excavated. 

 The distal joint of the toot about as long as the combined length of 

 the other two. The terminal toes are about as long as the distal joint 

 of the foot. At the base each toe is supplied with a small, sharp, lat- 

 eral spine. 



Length of lorica about 104 micro-millimetres; breadth, about 

 65 micro-millimetres. 



This species is very rare. Having seen it but once, I do not put 

 much stress upon the convex tongue seen upon the cephalad portion 

 of the ventral valve. I fear that that may be only a chance variation. 

 But the relative lengths of the joints of the feet, the relative length of 

 the toes, the spines at the base of the toes — all these are characters 

 which distinguish it from M. elliptica, its nearest ally. 



Family PTERODINADAE. 

 XIII. Genus Pterodina, Ehrenberg. 

 Sp. 21. Pterodina patina, Ehrenberg. 



Pterodina patina, Hudson and Gosse, The Rotifera or 



Wheel-animalcules, Vol. II, p. 112; pi. XXVI. fig. 11. 



Pterodina patina, C. L. Herrick, Bull. Sci. Lab. of 



Denison Univ., Vol. I, p. 59; pi. I, fig. 3. 



This species is very abundant around the roots of the duckweeds 

 {Lemnacea polyrrhiza, L.) of our larger ponds and canal basins. 



Family BRACHIONIDAE. 

 XIV. Genus Brachionus, Ehrenberg. 



Sp. 22. Brachionus pala, Ehrenberg 



Brachionus pala, * Hudson and Gosse, The Rotifera, or 



Wheel-animalcules; Vol. II, p. 117; pi. XXVII. fig. 3; and pi. 

 XXVIII, fig. 3. 



This species is occasionally encountered in one or two of our 

 shallow meadow pools. • The specimens encountered so far resemble 



