ORTMANN: monograph of the naiades of PENNSYLVANIA. 117 



L. H. D. 



Size: 1. Linesville, Cat. No. 61.874 121 mm. 67 mm. 39 mm. 



2. Shenango, Cat. No. 61.4218 91 " 55 " 29 " 



3. do. do. 87 " 53 " 28 " 



4. do. do. 50 " 31 " 12 " 



Soft parts (See Ortmann, 1912, p. 281). Glochidia (See Lea, Obs. VI, 1858, 

 PL 5, fig. 23; Ortmann, 1911, PI. 89, fig. 10; Surber, 1912, PL 3, fig. 44). Surber 

 gives the dimensions as 0.353 X 0.313 mm., while I found them to be: 0.34 X 0.28 

 mm. 



This species normally is hermaphroditic, and I never have found a specimen 

 in Pennsylvania having the male structure of the gills. However on rare occasions 

 individuals with male structure seem to turn up. I have recorded (19116, p. 309) 

 such a case from Lake Erie, but this has remained the only one. 



Breeding season: Gravid specimens were found on August 6, 1908; August 

 7, 1908; August 13, 1906; August 18, 1909; August 23, 1916; August 29, 1910; 

 Sept. 2, 1908; Sept. 3, 1908; Sept. 4, 1908; Sept. 7, 1908; Sept. 7, 1913; Sept. 

 10, 1906; Sept. 14, 1908; Sept. 18, 1916; Sept. 21, 1908; Sept. 27, 1909; Oct. 4, 

 1910; Oct. 10, 1907; Oct. 15, 1907; Oct. 19, 1908; and then again on IMay 14, 

 1908; May 22, 1908; May 23, 1908; June 2, 1908; June 17, 1909. The first 

 record for glochidia is on Sept. 7, while discharging specimens have been observed 

 on May 23, and June 2 and 17. 



Thus this species is clearly bradytidic, beginning to breed early in August, 

 gravidity lasting till May and June of the following year, when the glochidia are 

 discharged. The interim between two succeeding breeding seasons falls into the 

 second half of Jime and in July. 



Remarks: As to the specific name see the controversy between Frierson (1915, 

 p. 57) and Walker (1915, p. 74). 



This is a species easily recognized by the shape and color of the shell, and bj^ 

 the conformation of the hinge. It can only be confused with its nearest relative, 

 L. subviridis, but only in the young stage. Young specimens of L. viridis indeed 

 somewhat resemble older specimens of L. subviridis (Compare figs. 2 and 4, on 

 Plate IX) but they are always more distincth^ trapezoidal, with well-developed 

 posterior wing. In other respects the size of fuU-growTi specimens distinguishes 

 the two species at once. In Pennsylvania the geographical distribution is a good 

 diagnostic character, but this is not the case in New York, where the two species 

 overlap. 



There is not much variation in the shell. The posterior wing may be more or 

 less developed, and the shell may be more or less elevated at the upper posterior 



