INIO.— Plate XCII. 



iiKi/jncn in/lal(is <■( late rotiindatas fmnidd ct ancju- 

 latd, area, (lormli podkd plumdatd suico obscuro 

 latiuscido radiaid, margaritd albd ; deutibtis cardi- 

 iialibiis magiiis, uhUquis, coti/pirssis, cremdatis, acu- 

 vnnatk ; lamelUs lateraUbtis lonyk, ctirvatis. 



The glutted Unio. Shell thick, swollen, very inequi- 

 lateral, very narrowly rounded (yet peculiarly pro- 

 jecting) in front, somewhat winged truncated and 

 broadly biangulated behind, smooth, polished, of a 

 uniform dark brown (but olivaceous in the young) ; 

 li.H'ament short and thick ; umbonal ridge tumid and 

 angular towards the large swollen and broadly 

 rounded beaks, hinder dorsal area flattened and 

 rayed with a single obscure broadish furrow, nacre 

 white; primary teeth large, slanting, compressed, 

 creuulated, acuminated; lateral lamellaj long, curved. 



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

 Unio, vol. v. p. 21), pi. 17. f. 19. 



Hob. Louisiana, U. S. America. 



Species 502. (Copied from Lea.) 



Unio Pazii. TJh. iestd crammcald, valde inrTqmlaU'- 

 rali, lanceolald, antice vcidi'icosd ei latiure, posfice 

 gradaiim. depressd el curvato-citneifoi-mi, hifirne an- 

 tice arcuulini aeclivi, ad umhones Uimidd, lavi, oliva- 

 ced,fere n/idigi/e inconspicue radiaid, zo/ns incrementi 

 2 latis lideis reraoiisque ornatd ; nalibus injlalis fsa- 

 pitts eroaisj ; costd umbouali aiignlatd ; ared posticd 

 dorsali valde angudd, virente, liris iiicoiispicuis bira- 

 diatd ; liinuld bene impres-m, margaritd albd vel 

 albo-cixrulesceide ; dentibus cardinalibus lamellatis, [ 

 valde obliquis, corriigatis, in valvuld dextrd ningulis ; I 

 iamellis lateralibus productis, corrugatis. 



Paz's Unio. Shell thickish, very inequilateral, lanceo- 

 late, ventricose and broader in front, gradually dc- j 

 pressed and curved wedge-shaped behind, rising i 

 with an arched curve at the front ventral margin, 

 swollen at the umboes, smooth, olivaceous, almost | 

 everywhere indistinctly rayed, adorned with two dis- j 

 taut dirty yellow zones of increase; beaks inflated 

 (usually eroded), umbonal ridge angular ; hinder 

 dorsal area very narrow, dark green, with two indis- 

 tinct raised radiating lines; lunule well-marked, 

 nacre white or bluish-wliite ; primary teeth lamellar, 

 very oblique, wrinkled, single in the right valve ; la- 

 teral lamellfc produced, wrinkled. 



I.EA.. .lourii. Ac. Xat. Sc. ser. 2. vol. vi. (Obs. on Unio, 

 vol. xi.). p. fil. pi. 21. f (iO. 



Hab. Siam, China. 



I suspect is only a form of Ligallsianiis. 



Species 503. (Copied from Lea.) 



Unio Mouhotianus. Un. leatd tenui, depreasd, oblongd, 

 i)i(eqi(ilaterali, inferui siibrelusd, poslice rotwndalo- 

 subbiungulald, fiisco-lidescente concolore ; codd um- 

 bouali paulidmn elemtd el rotnndd ; ared dorsali pos- 

 licd angudd; nalibus j)rominulis ; margaritd albidd, 

 valde iridescenle ; dentibus cardinalibus minimis, lo- 

 batis ; lainelUs luteralibus tiullis. 



Mouhot's Unio. Shell thin, depressed, oblong, inequi- 

 lateral, somewhat indented below, rotundately sub- 

 biangular behind, of a uniform yellowish-brown ; um- 

 bonal ridge very slightly raised and rounded ; hinder 

 dorsal area narrow ; beaks slightly projecting ; nacre 

 ■whitish, very iridescent ; cardinal teeth very small, 

 lobed ; no lateral lamella;. 



Lea {Monocondylaa), Journ. Ac. N. Sc. Philad. ser. 2. vol. 

 vi. (Obs. on Unio, vol. xi.), p. Go. pi. 21. f 62. 



Hab. Laos Mountain, Cambodia. 



Allied to Baiiellii, but is less transverse, and less in- 

 equilateral. There are small obscure undulations on the 

 umbonal ridge. 



Species 50-t. (Copied from Lea.) 



Unio coxcavus. Un. tesld subtenui, -iiibvenlricosd, sub- 

 aquilaterali, ellipticd, antice satis late rotundatd, pos- 

 lice subangulatd, inferne arcuatd, lavi, politd, pallide 

 Itded, radiis viridibas mullis angu.slis pictd ; costd 

 umbonali inconspicud, aredposticd dorsali subangustd ; 

 inargarild albd ; dentibus cardinalibus compressis, in 

 nlrdque valvuld .singulis ; lamelUs lateralibus rectis, 

 longin.^c/ilis. 



The concave Unio. Shell thinnish, subventricose, sub- 

 equilateral, elliptic, rather broadly rounded iu front, 

 subangular behind, arched below, smooth, polished, 

 pale yellow, painted with numerous naiTow green 

 rays ; umbonal ridge inconspicuous, hinder dorsal 

 area rather narrow ; nacre white ; primary teeth com- 

 pressed, single in each valve ; lateral lamcllse straight, 

 longish. 



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

 vol. V. p. ir,), pi. 15. f. 11. 



Rab. S. Carolina, America. 



Des 



a single adult example 



