156 



NATURAL HISTORY OF VERMONT. 



Part L 



FRESH WATER AND LAND SHELLS. 



Remarks. — This species is more com- 

 pressed than any other native Planorbis, 

 the breadth being usually almost four 

 times the height; the regular double con- 

 vex form is also remarkable ; also its ten- 

 uity, a full grown specimen weighing on- 

 ly .05 of a grain. 



Planorbis parvus. — Say. 



DESCRiPTroN. — Shell brownish horn 

 color, feebly striate, shining ; whorls three 

 And ahalf or four, moderately increasing; 

 both sides concave, but the left more than 

 the right ; last whorl sabcarinate in the 

 middle ; inclination to the left about 40° ; 

 aperture subelliptical, slightly modified by 

 the intrusion of two thirds of the Jieight 

 of the penult whorl ; greatest breadth 

 O.2.") inch ; least breadth 0.2 inch ; height 

 0.07 inch. 



Remarks. — This species is found ])len- 

 tifully in a great variety of stations. 



Planorbis dejlectus. — Say. 



Description. — Shell horn color ; fine- 

 ly striate; whorls four; last whorl well 

 rounded, indistinctly carinate below ; 

 right side convex, flattened at the apex ; 

 left .side deeply concave ; suture deej) ; 

 inclination to tlie left about 4.5° ; aperture 

 round-ovate ; greatest breadth 0.17 inch ; 

 least breadth 0.13 inch; height 0.06 inch. 



Remarks. — The shell above described 

 is P. clevatus, Adams, which is probably 

 the young of Say's species. It is very 

 nearly allied to the preceding, but differs 

 in the elevation of the spire on the right 

 Bide, and deeper concavity of the left, and 

 in the absence of a medial carina ; the 

 last whorl is also often abruptly deflected 

 downwards. 



Planorbis hirsutus. — Gould. 



Description. -Shell horn-color, striate ; 

 epidermis green, with raised revolving 

 hirsute lines ; whorls three and a half, last 

 one strongly carinate in mature shells, 

 less so in the young, and in the former 

 often abruptly deflected downwards near 

 its termination ; right side with a small 

 narrow concavity ; left side sometimes 

 generally concave, sometimes like the 

 right ; inclination to the left about 40° to 

 50°, increasing with age; aperture nearly 

 orbicular, scarce!}' modified by the intru- 

 sion of the penult whorl. Greatest breadth 

 0.31 inch; least breadth 0.25 inch; height 

 0.] mch. 



Remarks. — The mature shell resem- 

 bles P. dcficctns, but is distinguished by 

 the medial carina of the outer whorl. It 

 very nearly resembles P. albus of Europe, 

 and probably is not specifically distinct. 



FAMILY COLIMACEA. 

 Genus Succinea. 



Generic Characters. — Shell ovale or ovate- 

 conic, uinber-colored ; aperture large, longer than 

 wide; outer lip shar|), never reflected ; columella 

 not folded, thin ; oi)ercuIum wanting ; animal wi:h 

 four tentacles, with the eyes at iheir summit as in 

 Helix. 



c 



-^ 



Succinea ohiiqua. — Sav. 



Description. — Shell ovate, striate ; 

 whorls three, oblique; spire half as long 

 as the aperture ; last whorl very large and 

 convex ; aperture ovate, nearly as broad 

 above as below, somewhat oblique. — • 

 Length 0.97 inch; breadth 0.55 inch ; di- 

 vergence 70°. 



Remarks. — In the New England states 

 this shell is generally of a deep umber 

 color, but in Ohio it is pale. It is found 

 in moist grounds, under stones and wood. 

 The animal is beautifully mottled with 

 dark purple on a cream-colored ground. 

 It goes into winter-quarters in October, 

 forming a thin transparent epiphragm. 

 The shell which we have described may 

 be S. campestris, Say, or more probably 

 the latter is only a variety of S. obliqua. 



Succinea oralis. — Say. 



Description. — Shell ovate, somewhat 

 conic, striate ; whorls three ; spire lesa 

 than one-third as long as the aperture, 

 small, conic ; last very large, elongate, 

 patulous ; aperture very large, exhibiting 

 much of the interior of the spire, ovate. 

 Length 0.61 inch ; breadth 0.3 inch ; di- 

 vergence 64°. 



Remarks. — This species is common 

 about the margins of water. It is ex- 

 tremely fragile. 



Succinea atara. — Say. 



Description. — Shell small, ovate, co- 

 nic, striate ; whorls three, very convex, 

 with the suture very deeply impressed ; 

 spire conic, five-sevenths as long as the 

 aperture, which is not large, ovate. — 

 Length 0.3 inch ; breadth 0.17 inch; di- 

 vergence 67°. 



Remarks. — The shell which Say de- 

 scribes under the name of .S'. vernicta is 

 probably the adult of this species. The 

 aperture is proportionally larger in the 

 young, as is also true of S. obliqua. When 

 young a viscid substance attaches dirt to 

 the shell, which becomes clean when 



mature. 



Genus Bulimus. 



Generic Characters. — Shell ovate, or oblong- 



