109 



A Revision axd Synonymy of the Parvis Groip of Uxioxid.?^:. (With 

 Six Plates.) By K. Ellsavorth Call. 



The tvpe of this group is a small unionine bivalve from the Fox river, 

 Wisconsin, eollected by Mr. H. R. Schoolcraft, while engaged in work on the 

 Northwest Expedition, of the early part of the present century. The type was 

 descrilied by Mr. D. H. Barnes, in 182), in the following words:* 



''Shell oblong-ovate, small, convex, sides rounded; beaks slightly elevated, 

 inside pearly white, iridescent. * * 



'•Diame'er, .35 — .525; length, .4- .(5; breath, .75 — 1.2. 



••Shell rather thin, beaks placed about one-fourth of the length from the 

 posterior extremity, ligament very narrow, anterior lunule distinct and obsoletely 

 ribbed; basal margin slightly .shortened; epidermis brownish; an obtuse, slightly 

 elevated rib from the beaks to the anterior basal margin; lateral tooth rectilinear 

 rounded at the end, and parallel to the base: nacre very brilliant." 



Ml'. Barnes completes his diagnosis of this form with the remark that it is 

 '•the smallest and most beautiful of all the genus yet discovered in America." 



In geographic distribution this small mollusk ranges from Western New York 

 and Florida, to Minnesota, Texas and Arkansas. In this wide range there are 

 numerous diverse environmental conditions, and the species appears, in a definite 

 sense, to have responded to these, and thus have been produced a number of 

 variations, which passing through the hands of difl'erent naturalists, have been 

 elevated into specific rank. In some cases, indicated below, the sexes have been 

 ' made to serve as the basis of new species; full series collected over the wide area 

 of distribution confirm the following synonymy./ in which the geographic distri- 

 l)Ution of several of the forms conveys its own argument : 

 tUxro PARVUS Barnes. 



Am. Jour, of Sci and Arts, 1st series. Vol. vi, IS.'H, p. 274, Fig. 18; Lea 

 figures the animal in .Jour. Phila. Acad. Nat. Sci., 2d series, \o]. iv, PI. xxix, 

 Figs. 102, 102a ; Conrad, Monography of Unio, 1836, PI. ix, Fig. 1 ; Reeve, 

 Conchologia Iconica, Vol. xvi, Unio PI. xxxv, Fig. 18fi, a very poor figure 

 from a specimen in the Museum Cuming. (PI. i. Figs. 1-3.) 



Unio paulii-t Lea. Trans. Am. Philos. Soc, Vol. viii, 1840, p. 213, PI, xv, 

 Fig. 20. From the Chattahoochee river, Cieorgia. (PI. ii. Figs. 11-13.) 



Unio minor Lea. Trans. Am. Philo.s. Soc, Vol. ix, 1843, p. 270, PI. xxxix, 

 Fig. 3. From Lakes Monroe and George, Florida. 



■ Aiiierienn .Jour, of Sci., 1st Ser., Vol. VI, No. 2, p. '274, pi. 1.3. fisr. 1^, outline only. 

 i The plate references in parentheses are to the several |>l!ites aecompanyliijr this article 

 The sexes are indicated on the plates. 



