UNIO.— Plate LVII. 



profimde angiilafo, manjim; dormti pmilulum arcualo, 

 (lerlim, margine lateridi obliquo, tcnnino suhcuneato, \ 

 iiiiirifiiif vfiitruVi pins iiihinxve recto, umbonlbus ovalihm, \ 

 linHiihiriil'ihi".. hevibi's ; latere antico brevi, angustn, 

 mnriiiiie itnrsitli auieiilo, declivi, tennino rotnndo. 

 The Tampico Unio. Shell subtrapezoidal, tiimid, thick, 

 smooth, covered with a solid, rather smooth, black 

 epidermis, violet within ; posterior side subquadratc, 

 with a deep ansile, dorsal margin a little arched, slo- 

 ping, lateral margin oblique, subeuneate at the end, 



ventral margin more or less straight, umboes oval, 

 prominent, smooth ; anterior side short, naiTOw, with 

 the dorsal margin cuneate, sloped, end rounded. 



Lea, Obs. on Unio, vol. ii. p. 34. pi. 7. f. IS. 

 Unio Tecomatnim, Lea, vol. iii. ib. 



Ihih. Tampico and Tecomate, in Mexico. 



The latter of the two shells is a little shorter and less 



quadrate than the one figured, but this may be expected 



to vary in individuals. 



