SEXUAL DIMORPHISM 



iri 



Upper Ohio. I do not feel, however, that the value of my conclus- 

 ions is greatly impaired thereby, as an equal number of shells of 

 both sexes from Lake Erie was included when this had to be done. 

 Besides the reduction 'to factors apparently expresses the relative 

 proportion of the part concerned, and, by the law of averages, 

 possibly evens up any great dijfferences. 



IV. — Bibliography. 



* 



1. Grier, N. M. "Morphological Features of Certain Mussel Shells 

 of L. Erie Compared with Corresponding Ones of the Upper Ohio Drain- 

 age." Annals Carnegie Museum, 1920. 



2. Hazy, J. "Die MoUusken Fauna von Budapest," III Biologischer 

 Theil, Malakozoologischer Blatter, 1881, p. 160, 161, 173. 



3. Israel, W. von. "Die Najadeen des Weidegebietes, etc." Beilage 

 zum Nachrichsblatt der Deutsschen Malakozoologischen Gesellschaft, N. 4, 

 1910, p. 4. 



4. Ortmann, A. E. "Monograph Najades of Pennsylvania," Mem. 

 Car. Museum, III, 191 1. 



5. Ortmann, A. E. " Notes on Family and Genera of Najades." Ann. 

 Carnegie Museum, VIII, 1912. 



6. Simpson, C. S. "A Descriptive Catalogue of the Najades." B. 

 Walker, Detroit, 1914. 



7. Utterback, W. I. "Naides of Missouri," Amer. Mid. Naturalist, 

 Vol. Ill, 1916. 



8. Walker, Bryant. "A Synopsis of the Classification of Fresh Water 

 MoUusca of N. America, North of Mexico, etc." University of Michigan, 

 Mus. Zoology Pub. No. 6, p. 171, 1918. 



TABLE I. 



GIVING AVERAGE DIMENSIONS OF MALE 



AND FEMALE SHELLS. 



SPECIMENS ""'5^'^'' 



27 Fusconaja flava 

 27 Fusconaja flava 



19 Amblema plicata 

 19 Amblema plicata 



TH. 

 DVL) 



9 .5294 -7756 .7749 -2315 -4867 .2499 .119 

 cf .4838 .7710 .7550 .2308 .544 .2001 .1181 



9 .409 .710 .806 .: 

 cf .437 .7680- .813 .iJ 



15 Pleurobema obliquumcoc 9 



15 Pleurobema obliquumcoc d^ 



15 Elliptio dilatatus 9 



15 Elliptio dilatatus d^ 



5 Symphynota costata 9 



5 Symphynota costata cf 



436 

 442 



297 

 304 



260 



287 



574 -184 .1398 

 565 .184 .1699 



