NAIADGEOGRAPHY OF MISSOURI 2~ 



a.2— MISSISSIPPI FLOOD PLAINS AND LOWLANDS (S. E. 



Mo. Depauperated Mussel Fauna). This region and the similar 

 one above (ai) are really separate from both the Ozarks (II) 

 and the Praities (I) since their ecologie conditions, i. e., the excess 

 of loess and other alluvia in their waters, are the causes of their 

 impoverished to extinct mussel faunae. 



The author would adopt the same nomenclature in this paper 

 as the one employed in his illustrated and descriptive catalogue 

 of the Naiades of Missouri.' It may be well to repeat here that 

 the radical changes from that of the Simpsoniau system 2 are due 

 to the acceptance of the Rafinesque Priority as recently revived 

 by Frierson,* Ortmann, 4 Vanatta 5 and other recognized students 

 of Naiades; also to a greater recognition of the nutritive and 

 reproductive structures of the soft parts than to the conchological 

 morphology as bases of classification; however, the writer would 

 not disregard the value of shell characters, yet does not cons'ider 

 their constancy so great for taxonomic purposes. In the following 

 list the progressive form of taxonomy is employed and, in most 

 cases, the Lindahl orthographic modification of Simpson and others 

 is used; however, it is thought that, instead of following the 

 uniform code of not capitalizing names for species in any case, 

 it would be more consistent with Latinic etymology to retain the 

 initial capital in all names of species derived from those of persons 

 when used substantively. 



For the sake of clearness the more familiar names, when 

 appearing as synonyms, follow the revised terms as equalities in 

 parentheses, but, in most cases, only the abbreviated name of the 

 author can appear for lack of space. In the accompanying list the 

 geographic distribution (Naiadgeography) of species and sub- 

 species is indicated thus: — • = scarce; X = fairly abundant; + = 

 abundant, as occuring individually; G = General Distribution 

 of Species. 



"American Midland Naturalist, Vol. IV, Plates I-XXIX, -1915-1916; 

 also special paper p. 519. 



-C. T. Simpson, Proc. U.S.Nat. Mus., XXII, pp. 504-1044, PI. XVIII, 

 1900b. 



3 L. S. Frierson, Nautilus, XXVIII, p. 6, May 1914; Footnote 5, Mid. 

 Nat., IV, p. 519. 



4 A. E. Ortmann, op cit., as collaborator. 



5 E. G. Vanatta, Proc. Acad. Nat. Sci. Phil., pp. 549~559» Dec. 8, 1915. 



6 Josua Lindahl, Jour. Cinn. Soc. Nat. Hist., 1906. 



