OJSr A NEW PEEITRICHOUS INFUSOEIAN. 293 



on the base, and the upper whorls are strongly spiralled. U. acuta, 

 Phil., from the Eed Sea, is smaller, with a less swoln body-whorl 

 and more tumid base ; the whorls of the spire are less tumid and 

 less exserted. B. Someri, de Folin, from the Cape Yerde Islands, 

 which is like in general aspect, is a much smaller, thicker, and 

 more spiralled shell, wath a less tumid body-whorl and more 

 regularly conical spire, the slope of the whorls being more flat- 

 tened ; the apex, too, is much fiuer. H. semistriata, D'Orb., 

 from Cuba, is shorter, broader, and less spiralled. H. auricidata, 

 Menard, which is perhaps as like as any, has not the contracted 

 base, and its extreme tip is O'OOi in. broad, while here the tip is 

 O'OOS in., or half as much. 



1 have called this species peracuta, because, though certainly 

 not very sharp, it is much more so than B. aouta, Phil. 



On a new Peritrichous Infusorian, Gerda caudata. 

 By Feedeeick W. Phillips, F.L.S. 



[Eead April 5, 1883.] 



The infusorian here recorded was found by me in water from a 

 pond at Hertford Heath, in company with large numbers of that 

 rather rare Eotifer CEcistes pilula. It is most nearly allied, and 

 is now provisionally attached, to the genus Gerda (the first genus 

 of the subfamily Vorticellina), which is thus diagnosed in Mr. 

 Saville Kent's recently published 'Manual of the Infusoria' : — 



" Animalcules solitary, elongate, subcylindrical, recumbent 

 upon, or simply adherent to, submerged bodies ; not possessing a 

 distinct sucker or specialized organ o£ attachment as in the genus 

 Scyphidia ; oral system including a peristomal border, vestibulum, 

 and ciliary disk as in the ordinary Vorticellcd ; increasing by lon- 

 gitudinal fission." 



The genus at present is limited to two species. The first, Gerda 

 fflans, was discovered by Claparede and Lachmann in vegetable 

 debris near Berlin, and is thus described : — 



" Body elongate, subcylindrical, highly contractile, three or 

 four times as long as broad, the wider posterior region during 

 contraction of a cup-like form; surface of the integument trans- 

 versely striate ; oral aperture narrow ; pharyngeal cleft deeply pro- 



