254 MEMOIRS OF THE CARNEGIE MUSEUM. 



L. H. D. 



Size: (Ohio-form) 1. Wiley, Cat. No. 61.3537 (sex ?) 165 mm. 121 mm. 57 mm. 



2. Godfrey, Cat. No. 61.4107 (cf ) 157 



3. Industry, Cat. No. 61.4416 (d") 118 



4. Industry, Cat. No. 61.3538 (9 gravid) .118 ' 



5. Cooks Ferry, Cat. No. 61.3540 ( 9 gravid) . 101 

 (Lake Erie-form) 6. Erie, Cat. No. 61.4102 (9 gravid) 91 



7. do. Cat. No. 61.3267 (d") 91 ' 



8. do. Cat. No. 61.4816 ( 9 ) 87 ' 



9. do. Cat. No. 61.4817 (cT) 75 



Soft parts (See Ortmann, 1912, p. 333). Glochidia: Lea (Obs. VI, 1858, PL 5, 

 fig. 25); Lefevi-e & Curtis, 1910, p. 97, fig. D, and PL 4, fig. 25; Ortmann, 1911&, 

 PL 89, fig. 18; Coker & Surber, 1911, PL 1, fig. 3; Lefevre & Curtis, 1912, p. 146, 

 fig. D; Surber, 1912, PL 1, fig. 8. My measurements of the glochidia are: 0.20 X 

 0.38; Lefevre & Curtis give: 0.23 X 0.41; and Surber: 0.220 X 0.380 mm. 



Breeding season: The following dates for gi-avid females are at hand: June 

 24, 1909 (eggs); August 29, 1908; Aug. 30, 1909; Sept. 6, 1914; Sept. 8, 1908; 

 Sept. 10, 1908; Sept. 15, 1913; Sept. 17, 1908; Sept. 17, 1913; Sept. 23, 1908; 

 Sept. 25, 1908; Sept. 28, 1911; Oct. 3, 1908. Then again in spring: May 21, 

 1909; May 22, 1914; May 23, 1914; May 24, 1911 (discharging); July 7, 1910 

 (discharging); July 8, 1910 (discharging); July 11, 1909 (discharging). 



The species seems to breed all the year round, and the breeding seasons appear 

 to overlap in June and July. Eggs have been found as early as June 24 (at Kelly) 

 but this might be an exceptional case. At the end of August fully developed 

 glochidia are present. On the other hand discharging females have been found 

 as late as July 11. These extreme dates refer to the Ohio-drainage. In Lake 

 Erie the time for discharging is the same, and I found females in this condition in 

 May as well as in the beginning of July. The beginning of the breeding season 

 has not been observed in the lake. 



Remarks: This is a species easily recognized by the large, winged shell, with 

 blackish epidermis, and purple nacre. In its external shape it much resembles 

 Lasmigona complanata (Barnes); while on the inside of the shell (hinge and nacre) 

 it is very different from it. 



Proptera alata varies greatly in outline, chiefly on account of the variability of 

 the wing. In old specimens, sometimes also in yoimg ones, the wing is almost 

 absent, and often it appears as if broken off in life. 



The form from Lake Erie is distinguishable from the Ohio-form. It is smaller, 

 darker brown (not black), has a lighter nacre, and is on the average slightly more 

 swollen. A greater regularity of the growth rests (as is usual in lake-shells) is 



