UN 10.— Plate XCVI. 



The Guarayos Unio. Shell not large, thick, veiitrirose, 

 very ine(|uilateral, rounded-oval, of a unilbrm brown, 

 wrinkled by concentric lamellar striae, arched below ; 

 liiiidi.T side ridged by two radiating folds, of which 

 the upper is the narrower, ronnded at its extremity ; 

 lieaks very pronunent, twisted; no lunule ; nacre 

 whitish or tinged with pale red ; liiiige-margin 

 broad ; in each valve a single cardinal tubercle, which 

 is compressed and very blunt; no lateral lamellae. 



D'Orbigny {Uonocomlijla'd), Moll. Amer. Mcrid. p. (iU. 

 pi. 08. f. 4 to 7. 



Hab. Guaravos, IVilivia. 



There are i\\ 



duh, 



.sulci bet 



iar fold 



Species 535. (Mus. Brit.) 



Unio Churgiulleanus. Un. testil tcnui, ili'jiresm (ml 



iiniLones nuhveiUricom), ohliqite ohmald, nnlwe perbreri 



ct mnximi courctalu, po-itice d'datntd et subalald, sitb- 



Itsvitjatd, luteo-mridi-chiercd, radiis vhx'titibiis paiwis 



lantum supra costam umbonalem subhumilem sparsim 

 ornatd ; marijine rentraJi antice abrttpte et subrecte 

 acclivi, postice scepius urcuaio ,■ nadbiis parvis, acutis, 

 incUnatis, liaud eminentibus ; martjantd argenled, 

 aliquando paululum nubrosfd ; dente cardinali parvo, 

 imico, compresso, trigorw ; lamellis laUralibim nullis. 



Churchill's Unio. Shell depressed (at the umboes 

 subveutricose), obliquely obovate, very short and 

 peculiarly contracted in front, dilated and somewhat 

 winged behind, nearly smooth, of an ashy greenish- 

 yellow, merely adorned here and there with a feu- 

 dark green rays beyond the scarcely elevated umbonal 

 ridge ; ventral edge rising abruptly and sonjewhat 

 straightly in front, usually arcuated behind; beaks 

 small, acute, inclined, not prominent ; nacre silvery 

 sometimes slightly pink ; cardinal tooth small, single, 

 compressed, triangular; no lateral laraellas. 



BouuGiGNAT, Rev. et Mag. Zool. 1857 (apart as Arae- 

 nites Malac. p. 35. pi. 2. f. 1 to 4). 



Hab. Anatolia. 



Almost a MonocondyUca. 



