1895. PROCEEDINGS OF THE NATIONAL MUSEUM. 



ing 17 whorls in a total length of 17.5 mm., against 18 whorls in a length 

 of 15.5 mm. for IT. microstoma. The last whorl in the present species 

 is ronnded below, tlmt of H. microstoma angnlated. H. vcracruziana 

 has the one and a half nuclear whorls polished, those of tlie ai)ical 

 cone finely ribbed, those of the rest of the spire striate, with a few 

 coarse riblets just behind the peristome. 



Locality. — IMizantla, Province of Vera Cruz, Mexico. 



Family BULIMULID.E. 



Genus BULIMULUS, Leach. 

 Subgenus PSEUDORHODEA, Dall. 



Shell slender, small, with a gyrate and pervious axis in the last 

 whorl and a half, without internal lamiuiB; jaw as in Thysanophora. 

 Type, Colmnna ramoitosa, J. Ct. Cooper, Lower California. 



This group has a superficial resemblance to the South American 

 Rhodea., Adams, but an anatomical examination shows it to be most 

 nearly related to the BnUmuli of the subgenus or section Leptobyrsus, 

 esx^ecially B. artcmcsia, Binney. 



BULIMULUS LEVIS, Dall. 



liulimulHS xaninsi var. levis, Dall, Proc. U. S. Nat. Mus., XVI, p. 641, 1893. — 

 Cooper, Proc. Cal. Acad. Sci., 2(1 ser., IV, p. 139, plr v, fig. 14. 



Fresh specimens sent by Dr. Cooper show this to be perfectly dis- 

 tinct from B. xantusi. 



BULIMULUS COOPERI, Dall. 



JiuHmnlus jyihtia, Crosse andFisCHER, not Binney; Cooper, Proc. Cal. Acad 

 Sci., 2d ser., IV, p. 139, pi. v, fig. 12, 1894. 



This form, distinguished among other things by pale peripheral band- 

 ing, is quite distinct from the true B. pilula of which the types are in 

 the National Museum. 



BULIMULUS BELDINGI, Cooper. 



Bulimidus hiscendens heldingi, J. G. Cooper, Proc. Cal. Acad. Sci., Ill, p. 209, 1892; 

 p. 340, pi. XIII, fig. .5, 1893. 

 An examination of specimens sent by Dr. Cooper fails to show inter- 

 mediate gradations between this species and B. inscemlens. I have no 

 doubt of its distinctness. 



Family UNIOISHD^. 



UNIO MITCHELLI, Simpson, new species. 



Shell rhomboidal, solid, rather inflated, rounded before, somewhat 

 biangulate behind; dorsal margin curved; incremental lines strong, 

 anteriorly irregular; epidermis varying from light brown to black, 

 coarse, often shining; beaks moderately prominent, showing traces of 



