U N I 



Plate XLIV. 



Species 339. (Mus. Sovverby.) 



Unjo ORBicaLATUS. Tin. testit crassd, orbiciilato-snhocali, 

 intus (did, ileniibus cardinalibus crassis, rngosis, den- 

 fidiis latfral'ibns lamina/is, solidis, extiis JIamde fnsco, 

 coHCi'iitrici dktaiiter rvyato, latere postico oblirpio, 

 sitbabrupte truncato, latare anlico brevissimo. 



The orbicular Unio. Shell thick, orbicularly subovate, 

 white within, cardinal teeth thick, i-ugose, latenil 

 teeth laminar, solid, yellowish-brown without, con- 

 centrically distantly wrinkled, posterior side oblique, 

 rather abruptly truncate, anterior side very short. 



HiLDRETU, in Silliman's Journal of Science. 

 Unio abriiptiis, Say. 

 Unio crassiis, Conrad. 



Hab. United States. 



Species 340. (Mus. Huuley.) 



Unio tenuisstmus. Un. tntd lenui, compressd, obliqid' 

 oblongo-ellipticd, inius pallida, denie cardiiwli in idrd- 

 tjiie valcd uibpromincnti, dentibiis lateralibus elonyatii, 

 hiiiiinatis uno et ditobns, extus Jlavido-viresceyiti, post 

 aiiguluhi viridi-nigricante, postice oblique lineatim 

 radiatd, latere anlico angmto, brevissimo, latere pos- 

 tico elongato, lalo, rotiindatim angulato, lermino acu- 

 minato, margine dorsali subelevato, delude declivi, 

 uiargine ventrali postice arcuato. 



The very tuin Unio. Shell thin, flat, obliquely oblong- 

 elliptical, pale within, with a ratlier prominent cardi- 

 nal tooth in eacli valve, lateral teeth elongated, lami- 

 nated one and two, outside yellow-greenish, very 

 dark green behind the angle, posteriorly obliquely 

 linearly rayed, anterior side narj-ow, very short, pos- 

 terior side elongated, wide, roundly angular, acumi- 

 nated at the end, dorsal margin rather raised, then 

 sloping, ventral margin posteriorly arched. 



Lea, Amer. Phil. Trans, vol. iii. t. 11. f. 31. 

 Unio purpurascens, Suains. 

 Unio velum, Say. 



Hab. lliverOhio. 



Species 311. (Miis. Hanley.) 

 Unio Scuwaktzexbaciiii. Un. lesld siibcgHndricd, ob- 

 luiigo-snbquadratd, iutns albido-carulesccnie, extus ob- 

 scure olivaced, latere anlico brevi, margine dorsali 

 recto, latere postico elongato obVupie angulato, lermino 

 oblique truncato, inargiue dorsali subelevato, area post- 

 augtdari sulcd obliqud impressd, margine ventrali recto, 

 uinbonibus angidatim rugatis. 

 Schwartzenbach's Unto. Shell subcylindrical, oblong- 

 subquadrate, bluish-wliite within, dull olive without, 

 anterior side short, with dorsal margin straight, pos- 

 terior side oblong, obliquely angular, obliquely trim- 

 cated at the end, dorsal margin rather raised, post- 

 angular area impressed with an oblique groove, ven- 

 tral margin straight, umboes angularly wrinkled. 



EOSSIASSLER. 



Hab. ? 



Species 343. (Mus. Sowerby.) 



Unio alatus. Un. testa compi-essd, laid, subovali, spn- 

 pliynottt, intus purpurea, dentibus cardinaUbus in 

 utruque valvd duobtis crenulatis, dentibus lateralibus 

 uno et duobus, laminatis, elongatis, extus viridi-nigres- 

 centi, concentrice subrugatd, peroblique obscure bian- 

 gidari, Icdere antico brevissimo, latere postico mngno, 

 margine dorsali perelevato, in alani magnam latampro- 

 ducto, margine ventrali injlato. 



The winged Unio. Shell compressed, wide, ratlier oval, 

 symphynote, purple within, cardinal teeth two in 

 each valve, wrinkled, lateral teeth one and two, lami- 

 nated, elongated, without blackish-green, concentri- 

 cally somewhat wrinkled, very obliquely obscurely 

 biangular, anterior side very short, posterior side 

 large, the dorsal margin much elevated, produced 

 into a large broad wing, ventral margin inflated. 



Say, Lea on Unio, vol. i. p. G3. 



Ihib. North America. 



May easily be known by the broadness of its marginal 



expansion and the bright purple colour of its nacre. 



August, ISGG. 



