GENUS VORTICELLA. 679 



the cuticular surface was shown, by a careful adjustment of the light, to be very 

 finely striate transversely, this ornamentation being more especially apparent in 

 specimens whose life was nearly extinct. These striations not being visible under 

 ordinary conditions, this type has been retained among the smooth-surfaced series. 



Vorticella cratera, S. K. PL. XXXIV. FIG. 22, AND PL. XLIX.- FIG. 14. 



Body broadly campanulate, inflated and hemispherical, the breadth 

 often two or three times greater than the total length; peristome-border 

 flattened and expanded, crateriform, often revolute ; ciliary disc but slightly 

 elevated ; parenchyma white, cuticular surface smooth ; pedicle stout, five 

 to seven or eight times the length of the body, contracting spirally. 

 Length -i -480". HAB. Fresh water, social. 



The above specific title is here proposed for the reception of the so-called Vorti- 

 cella patcllina of Ehrenberg, but which is entirely distinct from the essentially marine 

 animalcule upon which the same name was originally conferred by O. F. Miiller. 

 This latter form has been recently met with by the author, and is described in the 

 next paragraph. D'Udekem gives a highly characteristic drawing of the present 

 species in his ' Infusoires de Belgique,' as here reproduced, in which for the first 

 time full justice is done to the exceedingly elegant frill-like aspect presented by the 

 peristome-border in its typical expanded state. 



Vorticella patellina, Mull. 

 PL. XXXV. FIG. 26, AND PL. XLIX. FIG. 15. 



Body conical-campanulate in extension, widest at the anterior border, 

 and tapering thence in a straight line to its point of junction with the 

 pedicle ; pyriform with a puckered anterior margin when contracted ; the 

 diameter of the expanded frontal border equalling or but slightly less than 

 the total length of the body ; the peristome-edge exceedingly thin, expand- 

 ing in a flattened or rotate form around the frontal margin ; ciliary disc 

 but slightly elevated ; parenchyma transparent ; cuticular surface smooth ; 

 pedicle slender, three or four times the length of the body, contracting 

 spirally. Length 1-350". HAB. Salt water, social. 



The animalcule corresponding with the foregoing diagnosis was obtained by the 

 author, attached to algae and zoophytes, at Guernsey, in September 1871, and 

 evidently represents the true marine Vorticella patellina, as originally named and 

 figured by O. F. Miiller,* with which Ehrenberg and subsequent writers have pro- 

 posed to correlate the fresh-water type last described. The exceedingly straight 

 lateral walls, and consequently angular aspect of the bodies of this species, as pre- 

 sented during their most characteristic expanded state, distinguish it conspicuously 

 from all other representatives of the genus ; this lateral outline, joined to that of the 

 equally straight frontal border, communicates in fact to the animalcules, as seen 

 in optic section, the contour of an almost perfect equilateral triangle. 



Vorticella nutans, Mull. 

 PL. XXXIV. FIG. 28, AND PL. XLIX. FIG. 16. 



Body broadly campanulate in extension, nearly as wide as long, pyri- 

 form or globose when contracted, soft and elastic, cuticular surface smooth ; 



* ' Zoologia Danica,' 1776. 



