GASTEROPODA. 115 
Some incomplete specimens of Planorbis accord so exactly with 
the corpulent variety of P. trivolvis from Vermont, that I hesitate to 
regard them as distinct, though their broad separation in space would 
indicate it. They are thin and delicate, aud the whorl rises so much, 
when lying in the dextral position, that the aperture surmounts the 
preceding whorl by nearly one-third its height. They are also of a 
very light, almost white colour. More numerous and more perfect 
specimens are requisite for a more satisfactory decision, 
Puysa VENUSTULA (Gould). 
Testa parva, ovata, pellucida, nitidu, dilute cornea: spira elevata, anfrac- 
tibus quinque ventricosis, pustice subangulatis ; apertura ovata ; colu- 
mella valida, albida, vuldé sinuata. 
Physa venustula, Goutp; Proceed. Boston Soc. Nat. Hist., il. 215. 
June 1847. Expedition Shells, 43, 
AnimaL not so long as the shell, yellowish-green, tinted on the back 
and near the margin with blue; bencath, with a submarginal band of 
sky-blue, blending at the edges with green. Head short and transverse ; 
tentacles short and pale, mantle largely developed, with five or six 
deep digitations. 
SHELL small, ovate, shining, pellucid, very pale yellowish horn- 
colour; the spire is one-half the length of the aperture, of an acute 
form. Whorls five, ventricose, and slightly shouldered posteriorly- 
The aperture is ovate, the outer lip deviating a little from a regular 
curve bya slight inflection; the pillar lip is strong, whitish, and form- 
ing a conspicuous sinus as it joins the whorl above. There is a 
slight approach to an umbilical perforation. 
Length three-tenths of an inch; diameter three-twentieths of an 
inch. 
Obtained in the vicinity of Lima, Peru. Couthouy. 
This, though apparently a common species, I do not find to be de- 
