109 



A Revision and Synonymy of the Pakvis Groip of Inioniixk. (With 

 Six Plates.) Py K. Ellsworth C'ai-l. 



Tlu' type of this group is a small imioniiu' bivalve from the Fox river 

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

 Northwest Expedition, of the early j)art (tf the present century. The type was 

 described by Mr. D. H. Barnes, in 182), in the following words: ■' 



"Shell olilong-ovate, small, convex, sides rounded; beaks slightly elevated 

 inside pearly white, iridescent. * * •■■ 



■'Diameter, .:>i — .525; length, .4- .(i; 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." 



Mr. 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 different 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- 

 Ijution of several of the forms conveys its own argument : 

 tllNio PARVUS Barnes. 



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

 figures the animal in .lour. Phila. At'ad. Nat. Sci., 2d series. Vol. iv, PI. xxix, 

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

 C'onchologia Iconica, \'ol. xvi, Unio PI. xxxv. Fig. 18fi, a verv poor figure 

 from a specimen in the Museum Cuming. (I'l. i, Figs. 1-.3. ) 



Unio paid II !< Lea. Trans. Am. Philos. Soc, Vol. viii, 1840, p. 213, PL xv, 

 Fig. 29. From the Chattahoochee river, (Georgia. (PI. ii. Figs. 11-13.) 



Unio minor Lea. Trans. Am. Philos. Soc, Vol. ix, 1843, p. 27(), PI. xxxix, 

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



■•■ Aiiiei-iciin Jmir. ofSci., 1st Ser., Vol. VI, No. 2, p. 274, pi. 1.3. fig. IS, o„t/iiie only. 



f The plate references in parentheses are to tlie .-cveral |plales aeeompanyiiifi: lliis article 

 Tlie sexes are indicated on the plates. 



