ORTMANN: monograph of the naiades of PENNSYLVANIA. 127 



Soft parts (See Ortmann, 1912, p. 283). Glochidia (See Lea, Obs. VI, 1858, 

 PL 5, fig. 26; Lefevre & Curtis, 1910, p. 97, fig. B, and 1912, p. 146, fig. B; Surber, 

 1912, PI. 1, fig. 7). Surber gives the following dimensions: 0.385 X 0.390; Lefevre 

 & Curtis: 0.35 X 0.39; while I (1912) give: 0.34 X 0.37 mm. 



Breeding season: I have the following records for gravid females: August 3, 

 1909; Aug. 8, 1914; Aug. 9, 1907; Aug. 23, 1916; Aug. 29, 1910; Aug. 31, 1906; 

 Sept. 2, 1907; Sept. 2, 1908; Sept. 4, 1908; Sept. 5, 1908; Sept. 5, 1913; Sept. 7, 

 1908; Sept. 7, 1913; Sept. 10, 1906; Sept. 11, 1913; Sept. 12, 1913; Sept. 13, 

 1910; Sept. 13, 1915; Sept. 15, 1913; Sept. 17, 1912; Sept. 17, 1917; Sept. 18, 

 1917; Sept. 21, 1907; Sept. 21, 1908; Sept. 27, 1909; Sept. 28, 1911; Oct. 4, 1910; 

 Oct. 14, 1907; Oct. .15, 1907; Oct. 19, 1908; Oct. 23, 1907. Then again in spring: 

 April 22, 1908; April 24, 1908; May 11, 1907; May 11, 1911; May 13, 1910; 

 May 17, 1910; May 26, 1908. 



Thus this species is bradytictic. The breeding season begins early in August, 

 and by the end of this month (earliest date Aug. 31), and in September, glochidia 

 begin to be present. They are carried over the winter, and are found in the mar- 

 supium in April and May, and are discharged during May (observed on May 11 

 and 13). In June and July, there is an "interim," and although many specimens 

 were collected, there never was in these months a gravid female among them. 



Remarks: This species is easily recognized by the general shape, sculpture of 

 the posterior slope, and conformation of the hinge. From L. viridis, which it 

 resembles somewhat in shape, it differs also in bealv-sculpture. Variations are chiefly 

 due to differences in the relation of length to lieiglxt, and the development of the 

 sculpture of the posterior slope, which may be coarser or finer, and maj^ be more or 

 less distinct; but traces of this sculpture are always present. I have not been 

 able to discover any marked tendency in the direction of the development of local 

 races, unless it be in size, the forms of certain creeks always remaining compara- 

 tively small. This is especially true of some little streams in the mountains (upper 

 Loyalhanna River in Westmoreland Co., Quemahoning Creek in Somerset Co., 

 Little Mahoning Creek in Indiana Co.). Other small creeks, chiefly in the north- 

 western part of the state, favor the development of almost gigantic forms, for 

 instance, Little Beaver Creek, the upper Shenango River, and others. *- 



*- I found outside of our state in the upper Tygart River at Elkins, Randolph Co., West Virginia, a 

 rather interesting local form, with a very pronounced tendency toward the obliteration of the sculpture 

 of the posterior slope, which in these specimens in most cases is perfectly smooth, although individuals 

 occur, which show rudiments of the ribs. 



