92 THE NAUTILUS. 



GROUP A. WINTER BREEDERS. 



Truncilla triquetra Raf. Found gravid by the writer repeatedly 

 in the months of September and October. 



Truncilla perplexa rangiana Lea. Winter breeder (Sterki, '95). 

 Found gravid in September. 



Micromya fabalis Lea. July-August (Lea, III, '42). 



Lampsilis ventricosa Barn. Winter breeder (Sterki, '95); autumn 

 (Lea, III, '42); March, October (Lea, ibid.). Found gravid by the 

 writer in all months from May to October. Marsupium partly empty 

 (ovisacs extruded) on May 11; marsupium just beginning to be 

 filled, July 30. (Breeds apparently "all the year round." See 

 below.) 



Lampsilis ovata Say. Autumn (Lea, III, '42); November (Lea, 

 X, '63). Found gravid in August, September, October. (This is 

 merely a variety of L. ventricosa.) 



Lampsilis cariosa Say. October (Lea, II, '38). Found giavid 

 in August. 



Lampsilis ochracea Say. June and November (Lea, II, '38). 



Lampsilis multiradiata Lea. Autumn (Lea, III, '42); July, Au- 

 gust (Lea, ibid.). Found gravid in May, June, August, September, 

 October. Only few specimens being found in June and July, it is 

 uncertain whether there is an " interim " in the summer. 



Lampsilis luteola Lam. March, July-August, October (Lea, III, 

 '42); July (Baker, '98). I found gravid specimens in April, May, 

 June, July, August, September, October. The species is a typical 

 winter breeder, only the end of one season and the beginning of the 

 next partly overlap in summer. In June, and chiefly in the begin- 

 ning of July, sterile females (with the marsupium not charged) are 

 much more frequent than in other seasons, while gravid females are 

 very rare at the same time. 



Lampsilis radiata Gmel. "All the year round" (Conner, '07); 

 November (Lea, II, '38); May (Lea, X, '63). Discharge of ovi- 

 sacs observed from November to March (Lea, X, '63). 



Lampsilis ligamentina Lam. Winter breeder (Sterki, '95); au- 

 tumn (Lea, III, '42). Found gravid by the writer in August, 

 September, October, but not in July. Among numerous specimens 

 collected, July 8, '07, July 3, 10 and 13, '08, not a single gravid 

 female was discovered. The earliest date for the latter is August 3, 

 but from that time on they were found regularly. This species pre- 



