666 ORDER PERITRTCHA. 



Rhabdostyla sphaeroides, From. sp. Pl. XXXIII. Fig. io. 



Body when expanded forming through the dome-like elevation of the 

 ciliary disc, above the peristomal margin, an almost perfect sphere ; slightly 

 contracted beneath the peristome ; the cuticular surface smooth ; pharyngeal 

 cleft curved, greatly prolonged ; peristomal cilia long and stout ; pedicle 

 moderately stout, one-half the length of the body, considerably expanded 

 at both its distal and proximal extremities. Length of body 1-400". 



Hab. — Fresh water. 



While somewhat resembling the last species, it may be readily distinguished from 

 it by its smaller size and the dome-like elevation of the ciliary disc. According 

 to De Fromentel's illustration, the contractile vesicle is larger and located nearer the 

 centre instead of towards the peristomal region of the body as in the preceding 

 form. Its discoverer originally described this animalcule as a species of Epistylis. 



Rhabdostyla ringens, From. sp. Pl. XXXIV. Fig. i. 



Body elongate-conical or trumpet-shaped, attenuate, over twice as long 

 as broad, widest at the dilated anterior margin, gradually tapering towards 

 its point of juncture with the pedicle ; cuticular surface smooth, colour 

 brown ; pedicle short, slender, about one-third the length of the body. 

 Length of body 1-300'. Hab. — Fresh water. 



De Fromentel refers this species, under the title of Epistylis ringens, with doubt 

 to the Vorficella ringens of Chevalier, of which an illustration but no description has 

 yet been given. 



Rhabdostyla longipes, S. K. Pl. XXXIV. Fig. 29. 



Body elongate-campanulate, more attenuate posteriorly, about twice as 

 long as broad when expanded, symmetrically ovate in its contracted state ; 

 parenchyma transparent, finely granulate ; cuticular surface smooth ; pedicle 

 slender, sinuous, two or three times as long as the body, enclosing centrally 

 an even series of minute granular particles. Length of body 1-350". 



Hab. — Pond water, social. 



This species was found by the author in company with Vorficella campanula, in 

 February 1879, attached in small social patches to a Water Crowfoot taken from a 

 pond near St. Hehers, Jersey. The rigid footstalk in all cases enclosed, as repre- 

 sented in the accompanying illustration, an even line of granular particles most 

 nearly resembhng, except for the absence of colour, what obtains in Vorficella picia. 



Genus VI. PYXIDIUM, S. K. 



(Latin, pyxidium, a little box.) 



Animalcules solitary, ovate, adherent posteriorly through the medium 

 of a simple rigid pedicle ; ciliary disc, as in the genus Operctilaria, separate 

 from the peristome and attached to one side of the oral fossa. 



This genus is instituted for the reception of such solitary animalcules as accord 

 in structure with the zooids of the compound genus Opercularia, and towards which 

 it occupies the same near relationship that subsists between Rhabdosfyla and 

 Epistylis, or Vorficella and Carchesium. Two species only, both inhabiting fresh 

 water, have as yet been observed. 



