UNIO.— Plate XCIII. 



With the aspect and 

 he animal of Uiiio. 



Imost the hina;e of Cadaliii, but 



Species 508. (Mus. D'Orbigny iu Mus. Brit.) 



I'nio Solisiands. Un. testa, crassiusculd, subventricosd, 

 irueqidlaterali, rotundato-ovali, oUvaeed concolore, 

 conceutrlce rugatd; margine donali antico iiicurvato, 

 ad exlremitatem angulaio, lunula conspicnd instrudo ; 

 margine venfrali entice acclivi; costd umbonaU hu- 

 mili; ared dorsali posticd concavd,perangusld; nalibas 

 proniiuidis ; margaritd alio-ctsridescente ; dentibiis 

 cardiiialibiis binis, magnis, lamellalis, incurvatis, com- 

 pressin ; lauiellis lateralibus tenidssimis,Jlexiwsia. 



The Solisian Unio. Shell thickish, subventricose, in- 

 equilateral, rounded-oval, of a uniform olive-green, 

 concentrically wrinkle-ridged, front dorsal edge in- 

 curved, angulated at its extremity ; lunule well 

 marked ; ventral margin rising anteriorly ; umbonal 

 ridge not raised ; hinder dorsal area concave, verj' 

 narrow ; beaks slightly projecting ; nacre bluisli- 

 wliite ; primary teeth two, large, lamellar, incurved, 

 compressed ; lateral lamellae very thin, flexuous. 



D'Orbigny, Moll. Amer. Me'rid. p. 604. pi. fi9. f. 

 172-3. 



Hah. Buenos Ayres. 



The umboes exhibit a few slantingly divergent subni- 



diating ridges, which in the suborbicular form delineated 

 by D'Orbigny extend over the entire surface. 



Species 509. (Mus. D'Orbigny in Mus. Brit.) 



Unio Corrientesensis. Un. testa validd, ventricosd, 

 inaquilalerali, oblique obovali, antice brevi anyustd et 

 porrectd, subltsvigatd, olivaceo-liUeseeute vel virides- 

 cente, sape lineis virenlibus supra coslam umbonalem 

 iaconspicuam rotundatam radiatd ; margine ligamen- 

 tali arcuato, acclivi ; margine ventrali subatigulato, 

 antice praserlim acclivi; natibus eminentibus ; liinuld 

 perangustd, haud profundd ; margaritd ulbo-carules- 

 cente ; dentibiis cardinaUbus magnis, trigonis, tnher- 

 culiformibus, iu utrdqne valvuld singulis; lawellis 

 nullis. 



The Corrie>'TEs Unio. Shell strong, ventricose, in- 

 equilateral, obliquely oboval, short naiTOw but pe- 

 culiarly projecting in front, smoothish, greenish or 

 yellowish-olive, often with linear dark green rays be- 

 yond the inconspicuous rounded umbonal ridge ; liga- 

 mental margin arched and elevated; ventral margin 

 subangular, rising more especially in front ; beaks 

 prominent ; lunule veiy narrow, not profound ; nacre 

 bluish-white ; primary teeth large, trigonal, tuber- 

 cular, single in each valve ; no lamellse. 



D'Orbigny {Monocondylaa), Amer. Mcrid. Moll. p. 613. 

 pi. 68. f. 8, 9, 10. 



Hah. Argentine llepublic, S. America. 



