56 DESCRIPTION OF NEW 



Three An. edentula. All had charged oviducts. 



Four Unio calceolus. All had charged oviducts. 



One Unio planulatus. Oviducts charged. 



Four Unio luteolus. Two with charged oviducts. 



Several Unio crassus. Only one with charged oviducts. 



A few specimens of muUiplicatus^ tuberculatus, asperrimus, crassi- 

 dens, alatus, gracilis, &c., proved to be without oviducts ; doubtless all 

 being male. 



July 1835. — During this month examined some fifty or sixty speci- 

 mens of various species, in none of which did I find the oviducts 

 charged. 



Aug. 11,1 835. — Received three fine specimens of U. heterodon from 

 Mr Clark, of Manayunk. One of these was found to be charged nearly 

 the whole length of the branchiae with ova. These were so small as 

 to require the microscope to make them out. 



Sept. 6, 1835. — Opened a specimen of U. heterodon, found a few 

 days since in the Schuylkill. The oviducts were charged nearly the 

 whole length of the branchiae, and the ova very perceptible with the 

 microscope. 



Sept. 11, 1835. — Examined another U. heterodon, and found it simi- 

 lar to the last mentioned. 



Sept. 13, 1835. — Opened a number of various species. Found three 

 An. undulata, with their oviducts charged, being sufficiently forward 

 to exhibit very plainly their singular position across the lobe of the 

 branchiae. Also four Marg. undulata, with charged oviducts, but by 

 no means in a forward state. 



Dec. 13, 1835. — Examined a large Marg. margaritifera, which 

 proved to be without oviducts. Had a strong dorsal muscular attach- 

 ment. The palpi along the fringe of the mantle were more grouped 

 than those which I have observed on the Uniones. On the branchiae 

 were spots of a nankin yellow colour, quite consistent, but yielding to 

 the pressure of the knife. 



Also a large Marg. marginata, nearly three inches in width. This 

 had oviducts filled with minute ova, just perceptible with the micro- 

 scope. These two fine specimens were taken for me in Crum Creek, 



