Occasional Papers of the Miiseuin of Zoology 3 



and columella flexuose entire. Animal, with an opercuknn 

 membranaceous, head separated from the mantle inserted 

 above it, elongated, one tentaculum on each side at its base, 

 subulate acute, eyes lateral exterior at the base of the 

 tentacula. 



Six species are named bill, none described. 



2. In 1819, in his 'Trodome" published in the Journal de 

 Physique, etc., of Brussels, LXXXVIT, p. 423, Rafinesque re- 

 defined Pleurocera. Binney's translation (L. & F. W. Sh., Pt. 

 Ill, p. 62), with one or two exceptions, is excellent and is 

 as follows : 



.Shell spiral, oval or pyramidal, many whorls "en 

 aplomb'' (Binney says "rounded," rather flat or straight, 

 literally perpendicular) ; aperture oblong, oblique, base pro- 

 longed, twisted, narrowed above; outer lip thin, interior lip 

 appressed to the columella, which is smooth and twisted, 

 without umbilicus. Animal with a membranaceous oper- 

 culum, proboscis-like head, inserted in the back; tentacles 

 two, lateral, subulate, sharp, eyes at their exterior base. 

 Family Ncritacca (Binney says "Turbinacea"). Species 

 numerous, of which I have already twelve, all fluviatile, 

 from rivers and creeks. 



3. In 1820 (Ann. of Nat., p. 11), Rafinesque described his 

 Pleurocera I'errncosa. This is the first recognizable species de- 

 scribed as, or referred to, Pleurocera and is unquestionably 

 the species commonly known as Angitrema verrucosa. 



4. In his "Enumeration and Account," etc., 183 1, p. 2, 



Rafinesc^ue remarks : 



]My G. Pleurocera, 1819, is, perhaps, a S. G. of Melania, 

 but the animal is different, with lateral feelers; the shell 

 is always conical oblong with the opening oblong, oblique, 

 acute at both ends, columella flexuose twisted. 



In the same paper (p. 3), he described Pleurocera acuta 

 from Lake Erie. This species is undoubtedly the same as 

 Lea's Melania suhularis from the Niagara River as hereinafter 

 demonstrated. 



