366 MEMOIRS OF THE CARNEGIE MUSEUM. 



EXPLANATION OF PLATE XII. 



All figures are three-fourths natural size, a, lateral view; 6, dorsal view. 



Fig. L Alasmidonta (Prolasmidonta) heterodon (Lea). Adult male from the 

 Schuylkill Canal, Manayunk, Philadelphia Co., Pennsylvania, collected April 24, 1909; 

 C. M. Cat. No. 61.4250. 



Fig. 2. Alasmidonta (Prolasmidonta) heterodon (Lea). Adult gravid female from 

 the Schuylkill Canal, Manayunk, Philadelphia Co., Pennsylvania, collected April 24, 

 1909; C. M. Cat. No. 61.4250. 



Fig. 3. Alasmidonta {Decurambis) marginata (Say). Adult gravid female from 

 the Shenango River, Shenango, Mercer Co., Pennsylvania, collected September 27, 

 1909; C. M. Cat. No. 61.4270. 



Fig. 4. Alasmidonta {Decurambis) marginata susquehannoe Ortmann. Male from 

 the set of types, from the Susquehanna River, Selinsgrove, Snyder Co., Pennsylvania, 

 collected August 14, 1910; C. M. Cat. No. 61.4679. 



Fig. 5. Alasmidonta {Decurambis) varicosa (Lamarck). Adult female, from Prin- 

 cess Creek, Kunkletown, Monroe Co., Pennsylvania, collected June 14, 1910; C. M. 

 Cat. No. 61.4671. 



Fig. 6. Strophitus undulatus (Say). Specimen supposed to be this species, from 

 Delaware River, Newbold, Gloucester Co., New Jersey, collected by C. H. Conner; 

 C. M. Cat. No. 61.4135. 



Fig. 7. Strophitus edentulus (Say). Half-grown male, from a mill-race of Crooked 

 Creek, Tioga, Tioga Co., Pennsylvania, collected August 19, 1909; C. M. Cat. No. 

 61.4154. 



Fig. 8. Strophitus edentulus (Say). Adult gravid female, from Conneaut Outlet, 

 Conneautlake, Crawford Co., Pennsylvania, collected August 7, 1908; C. M. Cat. No. 

 61.3613. 



