278 MEMOIRS OF THE CARNEGIE MUSEUM. 



The species is said to grow even larger than the largest specimens listed above, 

 but Pennsylvanian specimens compare favorably with specimens from other 

 localities. 



Soft parts (See Lefevre & Curtis, 1910, PI. 1, fig. 5; 1912, PL 7, fig. 6; Ort- 

 mann, 1912, p. 344, fig. 24). Glochidia: Lea, Obs. VI, 1858, PI. 5, fig. 11; Lefevre 

 & Curtis, 1910, p. 97, fig. L; Ortmann, 19116, PL 89, fig. 21; Lefevre & Curtis, 

 1912, p. 146, fig. L; Surber, 1912, PL 2, fig.' 17. My measurements are: 0.22 X 

 0.28; those of Lefevre & Curtis: 0.20 X 0.24; those of Surber : 0.220 X 0.280 mm. 



Breeding season: I have the following records of gravid females: Aug. 13, 

 1907; Aug. 29, 1908; Aug. 30, 1909; Sept. 1, 1908; Sept. 3, 1908; Sept. 5, 1908; 

 Sept. 6, 1908; Sept. 7, 1914; Sept. 8, 1908; Sept. 11, 1913; Sept. 12, 1913; Sept. 

 14, 1915; Sept. 15, 1909; Sept. 17, 1913; Sept. 17, 1915; Sept. 22, 1910; Sept. 

 23, 1908; Sept. 24, 1917; Oct. 24, 1907; Oct. 24, 1910; Nov. 4, 1914; Nov. 12, 

 1911; and then again: May 21, 1909; May 22, 1909; May 23, 1914; May 25, 

 1914; July 5, 1909; July 10, 1908; July 23, 1907. 



Eggs have been found in August (earliest date Aug. 13). In September and 

 October specimens with glochidia are present, and then again in May. But all 

 three records in July refer to specimens with glochidia. Thus the breeding season 

 lasts from about the middle of August to the end of July, and may overlap with the 

 next, or there may be a short interval at the end of July and in the first half of 

 August. Surber found glochidia in September, October, November, in March, 

 April, and May, and then again in July, which agrees well with mj^ records. The 

 species is bradytictic. 



Remarks: Eurynia recta generally is easily recognized bj^ its large size, elon- 

 gated shape, and almost black color. However, young male specimens sometimes 

 resemble Elliptio dilatatus, but may be distinguished by the shining, green-black 

 epidermis, with indistinct, broad rays (if such are at all visible). Elliptio dilatatus 

 has a dull, more brownish-black epidermis, with fine rays (if such are at all visible). 

 The posterior end of E. recta is also more pointed, and the nacre is generally not 

 so deeply colored as in E. dilatatus. There are additional differences in the hinge- 

 teeth and the beak-sculpture. The female shell of E. recta cannot be confounded 

 with E. dilatatus, 



Eurynia recta is not very variable. The proportion of length and height 

 varies slightly, and so does the color of the epidermis and of the nacre. In Lake 

 Erie there is a local form, which differs from the Ohio type bj'' its smaller size, its 

 paler epidermis (browner, inclinding to russet), and more regular growth-lines. 

 But there are specimens in the lake, chiefly younger ones, which are indistinguish- 



