ORTM.INN: monograph of the naiades of PENNSYLVANIA. 237 



General distribution: Type locality, Ohio River (Lamarck). 



That this species favors the larger rivers seems to hold good throughout the 

 rest of its range, as well as in Pennsj4vania. It is found nevertheless in the north- 

 ern tributaries of the Ohio in Ohio, Indiana, and Illinois. In this region, it had a 

 chance to cross over into the lake-drainage, and is present in the Cuyahoga River 

 in Ohio (Dean, 1890, Dall & Simpson, 1895), in the Maumee-drainage in Ohio and 

 Indiana (Call, 1896o), and in the tributaries of Lake Michigan in Indiana (Call) 

 (See also our material). It is not fomid in the Michigan-drainage in Illinois, 

 although it ascends in the Desplaines River into the Chicago area (Baker, 1898a). 

 It occurs also in the southern part of Michigan (Walker, 1898) m the Lake Erie- 

 drainage, but is not in Lake Erie proper, and not in the lower St. Lawrence-drain- 

 g^gg 149 from Illinois it goes northward into Wisconsin (occurring also in the 

 lake-drainage at Racine, Racine Co., according to Call (1885) and Milwaukee, 

 according to Lapham (1860) and Minnesota (Call, 1885; Grant, 1886; Holzinger, 

 1888) and here apparently crossing over into the northern drainage in Manitoba 

 (Simpson, 1900) reported from Roseau River by Dawson (1875). Call (1895) 

 mentions it from Dakota, but the particulars are not known. It certainly occurs 

 in Iowa, disregarding the Mississippi (See Call, 1895; Marshall, 1895; Geiser, 

 1910), and the eastern part of Kansas (Scammon, 1906). 



It is also found present south of this range and is known from the southern 

 tributaries of the Ohio in West Virginia and eastern Kentucky, from which speci- 

 mens are before me. It is commonly reported from the Cumberland and Tennessee- 

 drainages, but here the var. gibba turns up, and particulars as to the mutual rela- 

 tion of the distribution of the two varieties are lacking. All the material, without 

 exception, which I collected in the upper Tennessee region in Tennessee and Vir- 

 ginia represents the form gibba. Wilson & Clark (1914) say that in the Cumber- 

 land River "chiefly the southern mucket" (gibba) is found. 



From ^Missouri southward into Arkansas ligamentina-f orms exist, and liga- 

 meniina has been reported from Missouri, for instance, by Utterback (1916) and 

 by Wheeler (1918) from the Ouachita in Arkansas. But, as has been stated, 

 different races (at least two of them) are found here, and these require further 

 study. In the Alabama-drainage, this tjqpe of Naiad seems to be entirely missing. 



'^'Simpson's record from Ontario (1900) is vague, but the Carnegie Museum has it from Ontario 

 north of Lake Erie (Grand River). 



