GENUS EUPLOTES. 799 



Euplotes harpa, Stein. Pl. XLIV. Fig. 22. 



Carapace elongate-oval, nearly twice as long as broad, the anterior 

 extremity widest, rounded, having a projecting tooth-like process at the 

 right-hand corner ; two similar but larger and blunter denticulations deve- 

 loped on the anterior margin of the ventral surface ; seven frontal and 

 nine scattered ventral styles ; five anal, and four isolated unbranched 

 postero-marginal setae ; the reflected or inner border of the peristome exten- 

 sively developed, finely ciliate ; eight straight longitudinal furrows travers- 

 ing the dorsal surface of the carapace. Length 1-168" to 1-144". 



Hab. — Salt water. 



This species, which is the largest representative of the genus, may be readily dis- 

 tinguished from the preceding type by the toothed edge of the lower surface of the 

 carapace, the reflected and ciliate peristomal border, and by the simple unbranched 

 character of the posterior marginal styles. 



Euplotes longipes, C. & L. 



Carapace elliptical, its right and left borders nearly straight and parallel 

 to one another, the anterior and posterior margins equally rounded ; the 

 front edge of the lower surface of the carapace simply curved, not denticu- 

 late ; no ciliated reflection of the peristome-border; the dorsal surface 

 smooth ; seven frontal and three ventral styles, the postero-marginal ones 

 unbranched. Length 1-180". Hab. — Salt water. 



Stein anticipates that this specimen may possibly be identical with his Euplotes 

 harpa. The author has, however, met with a form precisely agreeing with the 

 description given by Claparfede, in sea-water at Bognor, Sussex, in September 1873. 

 The even elliptical contour and undenticulate anterior ventral margin, together with 

 the simpler character of the peristome of the examples examined, assisted at 

 once in distinguishing it from Stein's type. 



Euplotes charon, Miill. sp. Pl. XLIV. Figs. 26-29. 



Carapace shortly oval or suborbicular ; the anterior and posterior 

 extremities obliquely truncate, parallel to one another; the right side 

 feebly but the left side strongly convex ; the dorsal surface usually ribbed 

 longitudinally; the anterior margin of the lower surface of the carapace 

 entire, or slightly indented ; the reflected peristome-border simply grooved, 

 uncinate ; seven frontal and three ventral styles ; the posterior marginal 

 setae small, unbranched. Length 1-320" to 1-260". 



Hab. — Salt and fresh water. 



The shorter and almost orbicular contour of the carapace of this species serves at 

 a glance to distinguish it from either of the preceding varieties, while from E. patella, 

 with which it is most likely to be confused, it substantially difters in the larger 

 number of the frontal styles and in the unbranched character of the postero-marginal 

 setre. Sharing the extensive or cosmopolitan distribution of the last-named type, it 

 is subject to considerable local variation, and more especially with reference to the 

 ornamentation of the dorsal surface of the carapace, and which, while usually more 

 or less extensively furrowed, is not unfrequently perfectly smooth. Examples derived 

 from salt water only have been observed to attain the larger of the two dimensions 



