UN 10 



Plate XXX II 



Species 170. (Miis. Cumiiin-.) 



Unio UMBROSUS. Uii. lesid eUiptica, subiiiflatd, obliqnu, 

 l<evi<jatd, inlus purjmred, extus obscure fmco-olicaced, 

 aiitice bred, rofui/dd, potsiice douyatd, obscitriis'tine bi- 

 angulald, margiiie dorsali roliiiidatini elevato, margbie 

 pont'ico-lalerali versus aiiyuhim posticiim. declivi. 



Thk shadowy Unio. Shell elliptical, subinflated, ob- 

 lique, smooth, purple within, obscurely olive-brown 

 without, sliort aud round in front, lengthened and 

 very obscurely biangulaled at the back, dorsal margin 

 roundly elevated, postico-lateral margin sloping to- 

 wards the posterior angle. 



Lea, Unio vi. pi. xxx. f. 26. 



Hub. The Medellin River, Mexico; Dr. Burrough. 



This smoothly elliptieal shell presents no striking cha- 

 racteristics, but is named from the dark colour of the epi- 

 dermis, which is probably accidental in the specimens de- 

 scribed. 



Species 171. 

 10 Medellixus. Vii. lesid siMrapezoided, obluti/jd, 

 Hiibcaiiipressd, iniiis pnrptired, extus leevigatd, Jusco- 

 olivaced, postice nigresceule, viridi obscure radiatd. 



margi, 



latere aittko breviusculo, migusto, viedio 

 subcontracto, latere postico ubiongo, o/jscure biuiigiilnfo, 

 inargiiie subelevato, versus angulum posticiini, declivi 

 inler angulos truncato. 



The IVIedellin Unio. Shell somewhat trapezoidal, ob- 

 long, subcompressed, purple within, smooth without, 

 olive-brown, dark and obscurely radiated with green 

 behind, anterior side rather short and narrow, middle 

 rather contracted at the margin, posterior side ob- 

 long, obscurely biangulated, margin somewhat raised, 

 sloping towards the posterior angle, and tiuucated 

 between the angles. 



Lea, Uuio ii. p. 39. pi. xii. fig. 34. 



Hub. River Medellin, near Vera Cruz ; Dr. J3urrou-li. 



Species 172. (Mus. Cuming.) 

 iELl. Un. tesld ohlougd, subellipt, 



pallidd, extus h-cite. 



inlus 

 trice sulcata, nigra, ct pos- 



lic'e jirojie uiuliones el versus inediun: tuberciilis obliquis 

 divergentibus obscure rugatd, latere antico brevi, sub- 

 rotundo, medio subcoiiiplai/aio, latere postico elougato, 

 obscure prope uiargiiieiu dvrsalem auguliito, area post 



uugus 



derlii: 



uargi. 



iH(li stibncu- 



inalo. 



Hembel's I'nio. Shell oblong, siibelliptical, pale within, 

 lightly concentrically suleated, and black without, 

 obscurely wrinkled with oblique diverging tubercles 

 behind, near the nmboes and towards the middle, 

 anterior side short, rather rounded, middle slightly 

 flattened, posterior side elongated, obscurely augn- 

 hited near the dorsal margin, area behind the angle 

 narrow, sloping, terminal margin rather acuminatetl. 

 Conrad, Men. U. p. 23. t. n\. 

 Ilab. Louisiana. 



Not unlike our liritish U. margaritifera, but the ven- 

 tral margin is not contracted in the middle, and the di- 

 verging tubercles placed obliquely on the hinder slope are 

 sullicient to distinguish the shell. 



fttiptira-snbtr. 

 M-/«,v olirarn 



Species 173. (Mus. Cuming.) 

 Unio LecontiaiNus. Uu. 



crassd, iujlald, iulus ah 



licvigald, latere antico brevi, rulundo, latere pusitco 



oblougo, iujlato, lato, obscurissime triangulalo, margiiie 



dorsali subelevato, margine termiuali oblique subtruii- 



rato. 



Leconte's IJxio. Shell elliptic-subtruueate, thick, in- 

 flated, orange within, olive-brown without, smootli, 

 anterior side short, rounded, posterior side ol)long, 

 inflated, wide, very obscurely triangidar, dorsal nuir- 

 giii slightly raised, terminal margin obliipiely sub- 

 truncate. 



Lea, Unio ii. p. 4-0. pi. xii. f 35. 



ILtb. River Georgia ; Major Lecunte. 



A much more tumid and truncate shell than I . umbrosus. 



Species 174. (Mus. Cuming.) 

 Unio si:ccisus. Uu. tedd subquadratd, trausverse sul- 

 cata, couipressd, iulus palUdi rosed, extus fusco-uigres- 



March, ISGG. 



