U N I 0. 



I'LATE XCIV. 



Species 510. (Mus. Hanley.) 

 Tnio scutum. IJn. tedd ct-assa, buequaUtcr snhveti- 

 tricosd, hi medio subretiisd, antice isubdepressd, valde 

 inayuilaterali, oblonyd, posiice obliquii subbiangidatd, 

 piced coHcolore, sublavigatd, margine ventrali retuso el 

 aiilicH acclivi, costd umbonuli elevata, ared poslicd 

 dorsali lata el concaviusciild, nalibiis vix promimdis, 

 margarild albo-Uvescente ; deniibm cardinalibus obli- 

 quis ; lamelUs laleralibus remotis. 

 The shield Unio. Shell thick, unei|ually subventri- 

 cose, somewhat indented in the middle, somewhat 

 depressed in front, very inequilateral, oblong, ob- 

 liquely siibbiaugular behind, of a uniform pitch- 

 colour, smoothish ; ventral edge refuse, rising in 

 front ; umbonal ridge elevated, the space behind it 

 broad and rather concave ; beaks but little projecting, 

 nacre livid whitish ; primary teeth slanting, lateral 

 lamellas distant. 

 Benson (teste Theobaldl. 

 Ifab. Tenasserim. 



The only individual known to us is in such bad condi- 

 tion that many of its characters are probably here omitted. 

 If identical with another undetermined shell from Pegu 

 (which is broader behind and not rctuse below), the 

 umboes are not sculptured, the epidermis is polished, the 

 ridge is rounded and well defined, and the smooth space 

 behind it rayed with one or two impressed lines, the 

 primary teeth (two in each valve) are wrinkled and nar- 

 rowly subtriaugular. 



Species 511. (Mus. Theobald.) 

 Unio L.4JIELL.4.TUS. Uii. testa tenui, in medio subveiitri- 

 cosu, alibi subdepressd, ovato-mbrhoinboided, inaqui- 

 lateraU, postice dilatatd, Icevi, nitidd, olivaced con- 

 colore ; margine dorsali utrinque siibrecto ; margine 

 ventrali suliarctiato, antice valde acclivi ; ared posticd 

 dorsali valde concavd ; ligammto maxima, lunuld 

 nulla, uatibns liand etiam prominulis, margaritd albo- 

 crerulesceute ; cardine utrinque lamellis laleralibus 

 (ad extremitates deorsum curvatis) instructo. 

 The lamellated Unio. Shell thin, somewhat ventri- 

 cose in the middle, elsewhere somewhat depressed, 

 ovate-subrhomboidal, ineqiulateral, dilated behind, 

 smooth, shining, uniform olive-coloured ; dorsal edge 



nearly straight on either side, ventral edge sub- 

 arcuated and much rising in front ; hinder dorsal area 

 very coucave, ligament very large, no lunule, beak- 

 uot even a little projecting, nacre bluish white : 

 hinge furnished on either side with lateral lamelke. 

 which are curved downwards at the extremities. 



Lea, Trans. Anier. Thil. Soe. ser. 2. vol. vi. (Obs. on 

 Unio, vol. ii. p. 19), pi. 6. f. 10. 



Hab. Pegu (Theobald) ; Bengal (Lea). 



A rare and remarkable shell, with a very peculiar hinge, 



quite different from the species erroneously so named in 



Plate LII. 



Species 513. (Mn.s. llaiiley.) 

 Unio coccineus. Uh. testa crassd, oblique rotandato- 

 snbqiiadratd, ad umbones eminentes venlricom, infenie 

 subdepressd, antice perbrevi, olivuceo-fuscd, nisi in 

 JHuioribus hand radiatd, vel Uevigatu, vel plicis obso- 

 letin incrementi iantum sculptd; margine cenlrali 

 subarcualo. antice acclioi ; natibus acutis, oblique in- 

 c urea lis ; lunuld conspiciid ; margaritd sa plus pall ide 

 rubra ; margine curdinali latissiino, denlibus crassis 

 verlicalibus corrugatis, laiiielhsque obliquis siibcurciitis 

 instructo. 

 The scarlet Unio. Shell thick, obliquely ruunded- 

 subquadrate, veutricose at the prominent umboes, 

 somewhat depressed below, very short in front, olive- 

 brown, not rayed except in tlie young, either smooth, 

 or only marked by the folds of increase ; ventral edge 

 subarcuated, rising in front; beaks acute, obliquely 

 incurved ; nacre usually pale pinkish-red ; hinge- 

 margin very broad, furnished with thick vertical 

 wrinkled teeth and oblique and somewhat curved 

 lamellae. 

 Hildreth, MSS. in Lea, Trans. Amcr. Phil. Soe. ser. 3. 

 vol. vi. (Obs. onUnio, vol. ii. p. 12),pl. :>. f. 1:.'. 

 U. calillus, Coin'ad. 

 llab. Ohio, N. America. 



This is quite distinct from the shell erroneously so 

 named in Plate XXII. The beaks are devoid of any pe- 

 culiar sulpture. 



October, 1SG8. 



