NO. 1205. syyoi'sis or THE \AiAi>KStnirt<>\. 667 



what radiately ridged ; laterals short, very imperfect, or wanting ;; beak 

 cavities deep, compressed. 



Animal with inner gills wider than the outer throughout ; palpi long; 

 inarsupium loose and flabby, and having ova scattered throughout it 

 in the only gravid specimen seen. 



t ALASMIDONTA UNDULATA Say. 



Monodonia undulata SAY, Nich. Enc., 1816, pi. in, fig. 3. 



* Alasmidonta undulata SAY, Jl. Acad. N. Sci. Phila., 1, 1818, p. 460. 

 Alasmodonta undulata SAY, Nich. Enc., IV, 1819, pi. in, fig. 3. * CONRAD, New 



F. W. Shells, 1834, p. 73. * FERCSSAC, Guer. Mag., 1835, p. 26. *C. B. 



ADAMS, F. W. ami L. S. of Vt., 1842, p. 15. 

 ^Alasmodon undulata SWAINSOX, Tr. ou Mai., 1840, p. 288, fig. 61. *GOULD, Inv. 



Mass., 1841, p. 115, fig. 76. *D KAY, Zool. of N. Y., Pt. 5, 1843, p. 198, pi. xv, 



fig. 227. 



^Margarita (Margarltana) undulata LEA, Syn., 1836, p. 44; 1838, p. 27. 

 " Unio undulata HAXLEY, Test. Moll., 1842, p. 211. * Biv. Shells, 1843, p. 211. 

 M<ir<jaritana undulata KITSTEK, Conch. Cab. Unio, 1862, p. 298, pi. xcix, fig. 4. 



"GOULD, Inv. Mass., 1870, p. 176, fig. 478." HARTMAX and MICIIENER, Conch. 



Cest., 1874, p. 92, tig. 190. *LATCHFORD, Tr. Ottawa F. N. Cl., 1882, p. 



54.* H. CARPENTER, Naut., IV, 1890, p. 47. * B. H. WRIGHT, Check List, 



1888.* P/ETEL, Conch. Sam., Ill, 1890, p. 174. 



'Marrjaron (Margaritana) undulata LEA, Syn., 1852. p. 42; 1870, p. 68. 

 *M\ja undulata WOOD, Ind. Test. Rev., 1856, p. 199, pi. I, snpp., fig. 5. 

 *JBapliia undulata H. and'A. ADAMS, Geu. Kec. Moll., II, 1857, p. 499. 



* Unio undulatus CATLOW and REEVE, Conch. Nom., 1845, p. 65. 

 *Strophitu8 undulatus STIMPSOX, Shells of New Eng., 1851, p. 15. 

 *1Unlo glabratns SOWKRBY, Rec. aud FOBS. Shells, XVI, 1823, fig. 

 Alasmodonta scitlptilis SAY, N. Harmony Uiss., II, 1829, p 339. FERUSSAC, Guer. 



Mag., 1835, p. 26. L. W. SAY, Terr, aud Fluv. Shells, 1840, p. 9. 

 *Strophitus sculptills STIMPSON, Shells of New Eng., 1851, p. 15. 



* Unio Itians VALEXCIEXXKS Rec. Obs. Zool , II, 1833, p. 235, pi. LIV, figs. 2, 2b. 



* Uniopsis radiata SWAIXSOX, Tr. on Mai., 1840, p. 1'89, fig. 62. 

 *Uniopsis mytiloidcs SWAIXSOX, Tr. on Mai., 1840, p. 382, fig. 62. 

 *$Unio swainsoni SOWERBY, Conch. Icon., XVI, 1868, pi. LXXVI, fig. 396. 

 *Maryaron (Margaritana) swainsoni LEA, Syn., 1870, p. 30. 



Lower St. Lawrence drainage; southward to North Carolina. 



Subgenus PEESSODON.A Simpson, 1900. 

 (Type, Unio calceolus Lea. 1 ) 



Shell decidedly rhomboid, surface generally painted with unbroken 

 rays; beak sculpture slightly corrugated; teeth compressed. 

 Animal with a thick, smooth, pad like marsupium. 



(Group of Alasmidonta calceola.) 



Shell small, subsolid, rhomboid, inflated, rayed but not shining; 

 beak sculpture varying from strong concentric bars to irregular corru- 

 gations, sometimes faintly doubly looped, and with fine radiating 



'The names Hemiodon, Hemiodonta, and Hemidon were applied by Swainson to 

 thie group, but he used the fir.st name previously for a division of the Helicidse. It 

 is better to apply a new name. 



