U N I 0. 



Plate LXXXVII. 



Species 464. (Copied from Conrad.) 



Unio constrictus. Uh. iedd hand mngnd, veutricosii, 

 elliptkn, subiiicequilakrali, olivnced, obscure racliatii, 

 sublavi, mnrgine tuntrali pontice incurvo, natibus e»ii- 

 nenUhm uttdulatisque, margaritd albidd; dentibim 

 cardinaUbus validis, erectis, subpyramidalibus ; Inm fi- 

 lls lateralibm satis brembns. 



The strained Unio. Shell not large, ventricose, ellip- 

 tic, somewhat inequilateral, olive, with obscure rays, 

 smoothish, incurved behind at the lower edge, beaks 

 projecting and undulated, nacre whitish ; primary 

 teeth strong, erect, subpyramidal ; latci'al lamiiiaj 

 moderately short. 



Conrad, Monog. Union. N. Am. pi. 49. f. 4 (errone- 

 ously in text, p. 91, as lienoKiis, var. constrictus, 

 corrected on Wrapper of Part II.). 



Ilab. North Eiver, Vu'ginia. 



" The posterior angle is much above the line of the 

 base. Several specimens exhibit the peculiar groove on 

 the posterior side, which has suggested the name." 

 (Conrad.) 



Species 465. (Brit. Mus.) 



Unio subtortus. Un. tesld sdidd, ventricosd, oblique 

 omtd, maxime iiiaquilaterali, subtortd, itiferni arcu- 

 atd, oUvaceo-fuscd, sericed, concenirice rugoso-striatd ; 

 costd umbonali consjncud ; ared posticd dorsali remote 

 et oblique uodoso-plicatd, umbonibus eminentibus et 

 poslice ad apices tuberculatis, margaritd albidd; 

 dentibus cardinaUbus crassis, dnplicibus, subvertica- 

 libus, sulcalis ; linnellis laleralibus elougatis, sub- 

 arcuatis. 



The somewhat-twisted Unio. Shell solid, ventricose, 

 obliquely ovate, peculiarly inequilateral, somewhat 

 twisted, arched at the ventral margin, olive-brown, 

 silky, concentrically wrinkle-striated, umbonal ridge 

 conspicuous ; hinder dorsal area with distant oblique 

 nodulous folds, umboes prominent and posteriorly 

 tuberculated at their tips, nacre whitish ; primary 

 teeth thick, two in each valve, almost vertical, 

 grooved ; lateral lamella; elongated, somewhat 

 curved. 



Baied and Adams, Proc. Zool. Soc. 1867. p. 4S;! 



36. f. 1. 

 Hub. Shanghai, North China. 



Species 466. (Mus. Hanley.) 



Unio Fontaineanus. Uh. tesid satis crassd, in i.tediu 

 coHvexd, nitidd, ufrinque depressd, oblique rotmiduiu- 

 obovatd, antice brevi angustatd liiisque incrementi 

 corrugatd, poslice dilatatd rolundato-quadrntd et sub- 

 Icevigatd, brunued concolore, margine ligamcutnli cur- 

 vato elevalo, margine vontrali antice rapiilc ai-rtin. 

 costd mubouali nulld, ared posticd dorsali concuciiis- 

 culd, sublcBvi, rugis elevatis obliquis perpaucis tautiim 

 iMtructd, umbonibus vix eminentibus, lunula anguste 

 lanceolatd, margaritd albo-crerrdescente, margine car- 

 dinali aiigusto, dentihus cardinaUbus laciniatis et sub- 

 laminatis, dentibus lateralibus arcuatis. 



Fontaine's Unio. Shell moderately thick, convex in 

 the middle, glossy, depressed at the sides, obliquely 

 rounded-obovate,anteriorlyshort,narrow,and wrinkled 

 by raised lines of growth, posteriorly dilated, rotun- 

 dately squared and almost smooth, rich brown, not 

 variegated, ligamental edge curved and elevated, ven- 

 tral edge rapidly rising in front, no umbonal ridge, 

 hinder dorsal area almost smooth, merely furnished 

 with a very few raised slanting wrinkles, iimboes 

 scarcely raised, lunule narrowly lanceolate, nacre 

 bluish-wliite, hinge-margin narrow, primary teeth 

 jagged and sublamiuar, lateral teeth arched. 



D'Orbigst, Voy. Ame'r. Mcrid. Moll. p. 605. pi. 09. 

 f. 6, 7 (.young). 

 U. roliiudiis, Moricand (not Spix). 



Hub. S. America. 



Pour South American shells, of somewhat similar shape, 

 having been delineated by their describers from immature 

 examples, have fallen into much confusion, — rolundus, Fon- 

 taineanus, variabilis, and membranaceus. The last does 

 not possess any teeth, and the last but one includes at 

 least two species : our reference to Maton's figures should 

 have excluded the transverse form. 



September, 18G8. 



