NATURAL SCIENCES OF PHILADELPHIA. 14* 



Observations. This shell is nearly allied to L. catascopium, Say, and perhaps 

 more nearly to L. intermedia, Mich., of Europe. From the former it maybe dis- 

 tinguished by being more fragile, more transverse, with a smaller, more 

 rapidly attenuating spire, but principally by the presence of an umbilical fis- 

 sure, which in catascopium is entirely concealed by the appression of the la- 

 bium. In this and other respects it is very near to L. intermedia, which, how- 

 ever, has a shorter spire, of fewer volutions. I name this species after my sister, 

 Mi33 Adeline S. Tryon, who has evinced much interest in conchological pursuits. 



5. LiMNyBA Traskii, Tryon, t. 1, f. 13. 



Description. Shell elongated, the spire drawn out and apex acute. Whorls 

 six, convex, almost shouldered, sutures deeply impressed. Aperture small, 

 oval, labrurn well rounded, labium slightly rounded, not appressed below, nor 

 covering the umbilicus, which, though small, is very distinct. Color light-horn 

 or cinereous. 



Dimensions. Length 16 mill., diam. 8 mill. Length of aperture 1 mill. ; 

 breadth 5 mill. 



Hah. Mountain Lake, California. Rev. J. Rowell. My cabinet and cabinet 

 of Mr. Rowell. 



Observations. At first I was disposed to regard this shell as a variety of L. 

 prozima, Lea, but a comparison with the type specimens of that species* shows 

 the following differences : the volutions are not so oblique, and are more 

 rounded, the aperture is also more rounded and the shell is umbilicated. 



Named in honor of Dr. J. B. Trask, one of the pioneers of California^ 

 Conchology. 



Limn^a caperata, Say. San Francisco. Oakland. 



LimnjEa fragilis, Linn. San Francisco. Mountain Lake. 



LiMNyBA umbrosa, Say. San Francisco. Mountain Lake. 

 LimNvBa reflexa, Say. Mountain Lake. 



C>. Physa Gabbii, Tryon, t. 1. f. 14. 



Description. Shell large, thin, closely striated by the lines of growth ; body 

 whorl inflated, its upper half flattened so that the labrum appears angulated in 

 the middle; spire moderate, apex acute, whorls six, convex, with distinct 

 sutures. 



Color light corneous, very much polished within ; lip margined with red. 



Dimensions. Length 25 mill., diam. 13 mill., length of aperture 15 mill 

 breadth 8 mill. 



Hob. Mountain Lake, California; Rev. J. Rowell. Santa Ana River, Los 

 Angelos Co., California; Wm. M. Gabb. My cabinet and cabinets of Mr 

 Rowell and Mr. Gabb. 



Observations. Several specimens of this fine large species were communicated 

 to me by my friend Mr.Wm. M. Gabb, after whom I take great pleasure in nam- 

 ing it. It is a much larger, thinner species than Ph. heterostropha, Say, and U at 

 once distinguished by the peculiar flattening of the superior portion of the 

 body whorl. The same character will also distinguish it from Ph. bullata. 

 Gould, in which species the aperture moreover is proportionately longer. 



Physa gyrina, Say. Mountain Lake. 

 Physa costata, Newcomb. Clear Lake. (Original loc.) 

 Physa humerosa, Gould. Colorado Desert. (Origual loc.) 

 Physa virgata, Gould. Santa Ana River, Los Angelos Co. 

 Physa heterostropha, Say. Dry Creek, Butte Co. Clear Lake, Centerville 

 Oakland. 



1. Ancylcb fragilis, Tryon, t. 1, f. 15. 



Description. Shell very small and fragile, sides nearly parallel or slightly in- 

 curved in the middle, but diverging anteriorly; ends rounded. Apex elevated 

 acute, curved backwards, with about two-thirds of the shell anterior to it 

 1863.] 



