FAMILY LIMNIAD.E PHYSA. 79 



Physa ANCILLARIA. 



PLATE V. FIG. 90. 



Physa ancillaria. Say, Jour. Acad. Nat. Sci. Vol. 5, p. 124. 

 P. id. Adams, Am. Journal Science, Vol. 40, p. 268. 



P. id. Godld, Invertebrata of Mass. p. 213, fig. 142. 



Description. Shell heterostrophe, subglobose. Whorls rather more than four, very rapidly 

 attenuated, smooth. Spire truncated, hardly elevated beyond the general curve of the surface. 

 Suture not impressed, very inconspicuous. Aperture but little shorter than the shell, dilated. 

 Lip a little thickened on the inner submargin. 



Color. Pale yellowish, occasionally deep bay : submargin of the lip reddish. Animal 

 lemon-yellow. 



Length, 0-5-0-6. 



This species occurs in Lake Champlain, and in other parts of the State. According to 

 Prof. Adams, the young of this species are not easily distinguished from P. gyrina, although 

 the mature specimens differ widely. 



Physa gyrina 1 



PLATE V. FIG. 87. 



(STATE COLLECTION.) 



Physa gyrina. Say, Journ. Acad. Nat. Sciences, Vol. 2, p. 171. 



P. id. Adams, American Journal of Science, Vol. 40, p. 268. 



Description. Shell sinistral, solid. Subovate. Whorls five or six, slightly convex, not 

 flattened, gradually tapering to an acute apex. Surface with minute incremental lines. Suture 

 slightly impressed. Columella with a slight fold above, turned over beneath the reverted 

 edge, and concealing the place of the umbilicus. Outer lip thin, acute. Aperture elongated, 

 acute above, more than one-half and less than two-thirds of the length of the shell. 



Color. Amber, often coated with a black pigment, except on the reflected portion of the 

 inner lip, which is polished. 



Length, 0'8; of aperture, 0'45. 



The specimens which I place here, were obtained from the northern part of the State by 

 Dr. Budd. They do not exactly coincide with any described species ; they approach nearest 

 to the descriptions of P. gyrina, which I have never seen. I have therefore placed it provi- 

 sionally here, to avoid the necessity of making a useless synonime. I annex the characters 

 assigned by Say to his P. gyrina. " Shell heterostrophe, oblong ; whorls five or six, gradually 

 acuminating to an acute apex ; suture slightly impressed ; aperture more than one-half, but 

 less than one-third of the length of the shell ; lip a little thickened on the inner margin. 

 Length rather less than an inch. Missouri." 



