ORTMANN: monograph of the naiades of PENNSYLVANIA. 215 



positively be determined by these characters. The females seem to remain smaller 

 than the males. 



L. H. D. 



Size: 1. Industry, Cat. No. 61.4423 (cf) 63 mm. 53 mm. 33 mm. 



2. Cooks Ferry, Cat. No. 61.3583 (cf ) 56 " 47 " 28 " 



3. Shippingport, Cat. No. 61.4756 (cf) 56 " 48 " 27 " 



4. Industry, Cat. No. 61.4122 (cf ) 46 " 38 " 22 " 



5. Industry, Cat. No. 61.3585 (9) 39 " 33 " 20 " 



No. 1 is the largest at hand, surpassing the maximum length given by Scam- 

 mon (1906). 



Soft parts figured by Lefevre & Curtis, 1910, PL 1, fig. 3; 1912, PI. 7, fig. 7; 

 described and figured by Ortmann, 1912, p. 310, fig. 16. Glochidia figured by 

 Lefevre & Curtis, 1910, p. 97, fig. M; 1912, p. 146, fig. M; Ortmann, 1912, PL 20, 

 fig. 1; Surber, 1912, PL 2, fig. 39. According to Lefevre & Curtis the measure- 

 ments are: 0.225 X 0.230; Surber: 0.225 X 0.235; Ortmann: 0.22 X 0.22 mm. 



Breeding season: According to Lefevre & Curtis (1912), and also Surber 

 (1912), the breeding season lasts from May to August: embryos are present from 

 the end of May to July 9, and glochidia from June 20 to Aug. 8. Thus this species 

 would appear to be tachytictic. 



I have specimens with glochidia (and discharging), collected on May 19, 1911; 

 June 20, 21, 22, 1911; July 13, 1911; July 29, 1914; and Aug. 6, 1910. These 

 accord with the breeding season as given above, with the exception of the first 

 date (May 19). This specimen is from Arkansas. It maj^ be an exceptionally 

 early date, or the breeding season may begin earlier in the South. 



It would be well to try to obtain additional data. The species is adapted to 

 a long breeding season. Being a rather primitive form, we may have here primitive 

 or transitional conditions; or on the other hand the breeding season may have 

 been re-adapted to more southern conditions, and may have become irregular. 



Remarks: A very peculiar, ancient type in the subfamily, which cannot be 

 mistaken for any other species on account of the peculiar shape and the unique 

 sculpture. It is rather variable in outline and color. 



There is a dwarf race in Lake Erie, light in color, which possibly deserves a 

 varietal name; but since this form has not as yet been fomid in Pennsylvania, I 

 shall not treat of it here. 



Localities in Pennsylvania represented in the Carnegie Museum: 



Ohio River, Shippingport, Cooks Ferry, and Industry, Beaver Co. 

 Monougahela River, Charleroi, Washington Co. (G. A. Ehrmann). 



