PHYSA. 485 



vaceous above, light feiTuginous beneath, long and thread-like. The 

 pouited lobes of tlie mantle are very conspicuous. 



The motions of the animal are very rapid, and it seems to move 

 with equal facility in an inverted posture, at the surface of the 

 water. 



The ova are excluded, enveloped in a gelatinous substance, about 

 twelve or fifteen in number, and of an egg-shaped form. In about 

 a fortnight they escape from the jelly, and move about Avitli great 

 rapidity. In fact, they are seen in motion for some time previous, 

 apparently struggling to disengage themselves from their nidus. 



This shell is everywhere to be found. Scarcely a brook or pool 

 is met with but some of these shells will be found in it. It is more 

 especially to be found in the running brooks. 



[Of this species I have seen specimens from Texas and Georgia, 

 and from as far north as Great Slave Lake. It ranges from the 

 Atlantic to the Pacific. It is our most common species. 



Physa ancillaria. 



Fig. 142. 



Shell ovate-globose, pale yellowish ; whorls four, smooth, suture not impressed ; 

 nperture nearly as long as the shell. 



Phym ancil/arin, Say, Journ. Acad. Nat. Sc. v. 124 (182.'5) ; Binnky's cd. 114. — Hal- 

 DKMAX, Mon. 27, pi. .3, tigs. 1 - 10 (184.3). — Goui.u, Iiiv. 213, fii:-. 142 (1841).— 

 Adams, Shells of VennoiU. 154 (1842). — De Kay, N. Y. Mull. 78, pi. .5, fig. 90 

 (1843). — CHE.UNITZ, 2d ed. 20, pi. 12, ti-s. 12, 13. — Chenu, Man. de Conch, ii. 

 480, fio. 3.550. — Axox. Can. Nar ii. 211, fig. ( 1857). — VV. G. Bixney, Smith. Inst. 

 L. and Fr. W. Sli-Us, ii. 81, fiff. 1,39 (1865). 



Ph>/sa obesa, De Kay, N. Y. Moll. 78, pi. 5, fig. 86 (1843). 



" Shell hcterostrophe, sub-globose, pale yellowish ; whorls rather 

 more than four, very rapidly attenuated ; spire truncated, 



£ Iff, f OO- 



hardly elevated beyond the general curve of the surface ; sut- 

 ure not impressed ; aperture but little shorter than the shell, 

 dilated ; labium a little thickened on the inner sub-margin." 

 (^Say.} Length, eleven twentieths of an inch; breadth, p. andi- 

 seven twentieths of an inch ; divergence, ninety degrees. 



Found in Connecticut and Merrimac Rivers, Fresh Pond, &c., to 

 Louisiana. 



Animal of a bright lemon color. 



This shell is distinguished from the preceding by its much shorter 

 spire, more angular outline, and especially by its suture, the margin 

 of one whorl being so closely and perfectly applied to the preceding 



