THE NAUTILUS. 5 



portance to the commercial shell buyer, are of undoubted inter- 

 est to the conchologist. These forms are Margaritana monodonta 

 Say, Hemilastena ambigua Say, and Anodonta imbecillis Say. 



Quadrula heros proved to be for this locality a fall breeder, 

 thus an exception to the summer breeding habit of other known 

 Quadrulas. Although the time of breeding is different, the evi- 

 dence obtained pointed to no change as to tachytlctic or short 

 breeding habit characteristic of the Quadrula group. October 

 seemed to be the principal breeding season, as an abundance of 

 gravid mussels was then obtainable. In November, among 

 many specimens examined, no gravid individuals could be 

 found. I have been interested to learn of cases of breeding 

 during later months. These come from localities further south, 1 

 and apparently are explainable on the basis of climate. There 

 is, however, the possibility of two breeding times in one season, 

 as has been claimed for some other short-period breeders, for 

 example, Margaritana margaritifera. I did obtain one breeding 

 in May from many examined, and a similar case is reported by 

 Lefevre and Curtis, who questioned the correctness of placing 

 this form among winter breeders. These cases seem, however, 

 to be very rare and quite exceptional. There is a difference 

 here, worthy of note I believe, in that the time of retention of 

 glochidia in Q. heros is relatively short as compared with other 

 winter breeders. I have given other observations upon this 

 mussel and a discussion of the literature in another paper, 2 so 

 need not cite them here. 



With the collections of Q. heros, Margaritana monodonta 

 seemed fairly abundant, so that I saw an opportunity to in- 

 vestigate the breeding of this species. Certain indications 

 pointed to an early spring breeding season, and in one expedi- 

 tion in search of it on March 10th, by reason of the collapse of 

 the ice, I came nearer to its place of abode than I cared to be. 



1 Mr. U. T. Utterbach reports gravid heros for January aud February, and 

 I desire here to acknowledge his kindness in submitting to me material and 

 notes. For other observations see Howard, A. D., 1914, "Experiments in 

 Propagation of Fresh-water Mussels of the Quadrula Group." Appendix to 

 the report of the U. S. Commissioner on Fisheries for 1913, pp. 1-52, 6 pis. 



'Howard, A. D., 1914, op. ., pp 28, 29. 



