650 ORDER PERITRICHA. 



Urceolaria mitra, Stein. PL. XXXI. FIG. 44 AND PL. XXXIII. FIG. 22. 



Body cylindrical or conical, its height when extended equal to about 

 twice its breadth, inclined at a considerable angle from its base of attach- 

 ment ; the anterior ciliary wreath somewhat obliquely set, capable of 

 being completely withdrawn within the substance of the body, the peri- 

 stome then contracting over it ; pharyngeal cleft conspicuous, produced 

 through about one-half of the extent of the body ; the contractile vesicle 

 stationed near the centre of this cleft ; endoplast posteriorly situated, 

 linear, curved. Length of extended body 1-1600". 



HAB. Fresh water, on Planaria torva. 



As originally pointed out by Claparede and Lachmann, the figure and description 

 of this species given by Stein,* reproduced at PI. XXXIII. Fig. 22, in which cilia are 

 represented as forming a marginal band on each side of the anterior portion and dis- 

 posed at right angles to those of the posterior wreath, is a misinterpretation, the 

 anterior ciliary system agreeing essentially with that of Trichodina pediculus, except- 

 ing that the disc as a whole is somewhat obliquely tilted. Stein, in his more 

 subsequent writings, has fully recognized the accuracy of this emendation of the 

 diagnosis of the species on the part of the Swiss authorities. 



GENUS III. CYCLOCH^ETA, Jackson. 



Animalcules free-swimming, discoidal or turban-shaped, the ventral 

 surface forming a circular adherent sucker, as in Trichodina, its margin 

 bordered with a fringe of locomotive cilia, and strengthened interiorly by 

 a toothed horny ring ; oral aperture situated laterally in the angle formed 

 by the junction of the body with the adherent disc, not associated with 

 a buccal ciliary spire, but continued deeply into the substance of the body 

 as a finely ciliated pharynx ; a row of long, erect, bristle-like appendages 

 forming a circle round the body immediately behind the border of the 

 acetabulum. 



The distinction of the type form of this genus from Trichodina and Urceolaria 

 consists in the absence of the anterior adoral groove and spire of cilia, which 

 would appear to be entirely obliterated, but is perhaps to a certain extent replaced 

 by the more posterior circlet of long, erect setae. On the other hand, however, as 

 suggested by its discoverer, these abnormally developed setae would seem to coincide 

 to some extent with the characteristic equatorial girdle of setose springing-hairs 

 of the genus Halteria. 



Cycloehaeta spongillse, Jackson. PL. XXXIII. FIGS. 23 AND 24. 



Body elastic and changeable in form, usually depressed, turban-shaped, 

 about twice as broad as high ; pharynx produced inwards to the centre of the 

 body, its interior wall finely ciliate ; the horny ring within the adherent disc 

 apparently forming one continuous piece having thirty-seven short external 

 booklets, and an equal number of long, slender, inwardly projecting radii ; 

 posterior setae sixteen in number, forming an erect fringe whose altitude 

 equals about twice that of the body ; contractile vesicle situated a little 



* 'Die Infusionsthiere,' 1854. 



