UNIO.— Plate XCI. 



Remarkable for its high acutely angular umboual ridge, 

 and flattened sides. 



Species 495. (Copied from Lea.) 



Umo Sapotalensis. Un. tesld crasad, uld anlici ven- 

 tricosa, ad umbones autem planiilaid, inesqiiilaierali, 

 subovali, hiferne retimt, postice subbiangitlaln, luted, 

 liiieis permidlk viridibiis undlqiw radiatd ; coda um- 

 bonali subcarinatd, natibus vice prominuUs, margaritd 

 subaured ei pulc/ierrime iridescenle ; dentibm cardl- 

 nalibus satis magnis, in valvidd dextrd singulis ; la- 

 tuellis laterulibas magnis, remotis, rectiusculis. 



The Sapotal Unio. Shell thick, ventricose except in 

 front, yet flattened at the umboes, inequilateral, sub- 

 oval, indented below, subbiangular behind, yellow, 

 everywhere rayed with very numerous green lines ; 

 umbonal ridge siibcarinated, beaks scarcely project- 

 ing, nacre of a somewhat golden yellow, and beauti- 

 fully iridescent ; primary teeth moderately large, 

 single in the right valve ; lateral lamella' large, dis- 

 tant, straightish. 



Lea, Trans. Amer. Phil. Soc. ser. 2. vol. viii. (Obs. on 

 Unio, vol. iii. p. 71), pi. 21. f. 47. 



JJob. Sapotal river, Tlouotalpaui, Mexico. 



riilge subanguhir, liiuder dorsal area broadish ; beaks 

 a little projecting, compressed, the tips with a double 

 row of concentric uudulatious, nacre white ; primary 

 teeth rather small, lamellar, single in the right vtilve ; 

 lateral lamelkc short and straight. 



Lea, Trans. Amer. Phil. Soc. ser. 2. vol. x. (Obs. on 

 Unio, vol. v. p. 13), pi. 13. f. fi. 



Jlab. S. Carolina, America. 



This pretty shell, which reminds one of f'. jiresnus 

 {Symphonota compnasa), is somewhat disposed to be 

 winged. 



Species 496. (Copied from Lea.) 

 Unio decokatus. Uit. testa subtemii, depn'ssiascidd, 

 subovatd, iubinmqiiilaterali, infirnh vi.i- retiisii, viridi- 

 Jlavescente, radibs capillaribiis uiiil/i-i /'■/•>■ lunliijiie or- 

 natd, lavi; costd umbonali suiuiiynlutii, ami dorsali 

 posticd latiusculd ; natibus promiiiidis, compressis, ad 

 apices undulai'um serie diiplici concentrice iiistnictis, 

 ■margaritd albd ; dentibus cardinalibits satis purcis, la- 

 mellaribus, in valvuld dextrd siiigidis ; lamcliis hilc- 

 ralibus brevibus, rectis. 

 The adorned Ukio. Shell thinuish, rather depressed, 

 subovate, somewhat inequilateral, scarcely indented 

 below, yellowish-green, almost everywhere adorned 

 with numerous capillary rays, smooth ; umbonal 



Species 497. (Mus. D'Orbigny in Mns. Brit.) 



Unio Mixuanls. Un. testa crassd, veutricosd, subinee- 

 qiuluteruli, oblique subovali, subrhombed, antice an- 

 gustd sed porrectd, suUavigatd, cinereo-luteo-virides- 

 cente, liueis vireutibus supra costam umbonalem rotun- 

 1 datam. radiald ; margiiw dorsali autico perJiumili, 



brevi, incun-ato-acclivi, ad extremitatem anyulato ; 

 lunuld magnd el maxime profundd ; margine ventrali 

 subarcuato, antice acclivi; timbonibus eininentibus, na- 

 tibus acutis infiexisque, margaritd argented ; cardine 

 111 in fossiculifero, tubercuUs autem magis lamellatis. 



The Minuan Umo. Shell thick, ventricose, rather in- 

 equilateral, obliquely suboval, subrhombie, narrow 

 yet peculiarly jutting out in front, smoothish, ashy 

 yellowish-green, with dark green linear I'ays beyond 

 the rounded umbonal ridge ; front dorsal edge very 

 low, short, incurvately rising, angulated at its extre- 

 mity ; lunule large and very profound ; ventral mar- 

 gin subarcuated, rising in front; umboes prominent, 

 beaks acute and inflexed, nacre silvery ; hinge as in 

 fossicnliferus, but tubercles more laminar. 



D'OuiilGNY [Monocondglcea), Amer. Mi'rid. Moll. p. C12. 

 pi. 70. f. 8, 9, lU. 

 U. Parchappii, D'Orb. 



Hab. La Plata. 



Li Parchappii (from the Argentine Eepublic) the nacre 

 has a somewhat oranare tint. 



