Chap. 6. 



INVERTEBRAL ANIMALS OF VERMONT. 



167 



FRESH WATER AND LAND SHELLS. 



Unio complanatus. — Lea. 



Description. — Shell oblong, rather 

 thick ; epidermis blackish or greenish 

 brown, sometimes yellowish, with numer- 

 ous irregular green raj's ; striae of growth 

 rather coarse ; beaks rather prominent, 

 small ; discs compressed, sometimes con- 

 siderably inflated, but always flattened ; 

 anterior side from one-fifth to one-third 

 as long as the posterior ; hinge margin 

 nearly straight ; posterior margin a little 

 curved, oblique; inferior margin straight, 

 sometimes a little incurved or excurved ; 

 anterior margin well rounded ; nacre pur- 

 plish red, pink, sometimes light salmon 

 color, rarely white; lamellar teeth nearly 

 straight; cardinal teeth double. Dimen- 

 sions of three specimens: No. 1, length 

 3.9 inches; height 2 inches; width 1.4 

 inch. No. 2, length 3 inches ; height 

 1.53 inch; width o's inch. No. 3, length 

 3.05 inches; height 1.53 inch; width 1.36 

 inch. 



Remarks. — This species is subject to 

 great variations of form, of which the 

 most remarkable in this state is that of a 

 gibbous variety in- lake Cliamplain. No. 

 3 is an example ; No. 2 exhibiting on the 

 contrary a very compressed form. This 

 species is the most common of tlie Naia- 

 des in this, as in the otlier New England 

 states. Immense numbers cover tlie shores 

 of lake Champlain. 



Unio siliquoideiis. — Bar.nes. 



Description. — Shell ovate, not very 

 thick ; epidermis yellowisli or somewhat 

 greenish brown, with numerous irregular 

 green rays, shining ; stria) of growth us- 

 ually rather fine ; beaks small, rather 

 prominent, wrinkled ; discs convex, tu- 

 mid; anterior side a little more or less 

 than one-third as long as the posterior ; 

 inferior margin sometimes curved, some- 

 times straight; other margins rounded; 

 nacre clear white, sometimes ligiit salmon 

 color ; cardinal teeth equally bifid in the 

 left valve, unequally in the other ; lateral 

 teeth a little curved, not long. Dimen- 

 sions of three specimens : No. 1, length 

 2.7 inches; height 1.9 inch; width 1.3 

 inch. No. 2, length 2.43 inches ; height 

 1.3 inch; width 0.85 inch. No. 3, length 

 3.05 inches ; height 1.65 inch ; width 1.4 

 inch. 



Remarks. — This species, allhough al- 

 ways ovate, varies much in the ratios of 

 the three dimensions. To illustrate this, 

 the above measurements are taken from 

 examples of the greatest extremes ; No. 

 1, of height; No. 2, of length ; and No". 3, 

 of width. The largest individuals are 

 about 4 inches in length. According to 

 Mr. Lea this species is U. lutcoltis, La- 



marck, and the latter name lias the right 

 of priority ; but according to others, La- 

 marck's species above quoted is U. cario- 

 sus, Say. We therefore, provisionally, 

 give the preference to the name affixed 

 by Mr. Barnes. 



Unio vcntricosus. — Barnes. 



Description. — Shell short, ovate, not 

 very thick ; epidermis usually pale yel- 

 lowish brown, with green rays, of very 

 unequal width, sometimes numerous, of- 

 ten obsolete, except on the corselet ; 

 smooth and shining; beaks large and 

 prominent, wrinkled ; umbones very tu- 

 mid, with a more or less distinct angle 

 extending to the bottom of the posterior 

 margin ; discs convex ; anterior side about 

 half as long as the posterior; hinge mar- 

 gin sinuous ; posterior e.xtremity irregu- 

 larly rounded, in the females high and 

 truncate, in tiie males somewhat tapering 

 and produced ; inferior margin more or 

 less rounded ; anterior extremity depress- 

 ed, well rounded ; nacre wiiitc ; cardinal 

 teeth not large, deeply bifid ; lamellar 

 short, distant from the beaks. Dimen- 

 sions of three specimens: No. 1, length 

 5.5 inches ; height 3.3 inches ; width 2.3 

 inches. No. 2, length 3.35 inches; height 

 2.35 inches ; width 1.77 inch. No. 3, 

 length 3.8 inches; height 2.3 inch. : width 

 1.83 inch. 



Remarks. — The variations of form are 

 for the most part those of sex, as exhibit- 

 ed in the above measurements. Nos. 1 

 and 3 are males, No. 1 being unusually 

 larofe. No. 2 is a female. This species is 

 not rare in lake Chami)lain, which is its 

 most eastern limit. It is common in the 

 western states. 



Unio rectus — Lamarck. 



Description. — Shell very long ovate, 

 thick ; epidermis olivaceous above or 

 throughout, usually yellowish brown be- 

 low, but nearly covered with dark, broad, 

 more or less confluent, green rays; beaks 

 rather prominent, smooth ; discs moder- 

 ately inflated, scarcely convex; anterior 

 side about one third as long as the poste- 

 rior ; hinge margin slightly curved ; pos- 

 terior extremity sub-rostrate ; inferior 

 somewhat curved, straight, or in females 

 incurved ; anterior margin rounded ; na- 

 cre white, pink above ; cardinal teeth 

 pink, double, both divisions stout on the 

 left valve, also the inner one on the right. 

 Lengtli 5.75 inches ; height 2.3 inches ; 

 width 1.55 inch. 



Remarks. — This species is common in 

 the western states, and has its most east- 

 ern limit in lake Champlain, where it is 

 rare. The females are much higher in 

 the posterior half, in consequence of a de- 

 velopment of the inferior margin. 



