61 



with interrupted undulations; concentric lines promi- 

 nent; epidermis dark olive, obscurely rayed, wrinkled 

 on the margins; cardinal teeth double in both valves, 

 slightly compressed, oblique, striated; nacre varying 

 from bluish white to deep salmon or purple; cavity 

 most capacious under the umbonial slope. 



SYNONYMES. 



U. lienosus, Nob. Silliman's Journal, vol. xxv. p. 339, pi. 1, 



fig. 4. 

 U. Nashvillianus, Lea. Trans. Amer. Phil. Soc, (new series,) 



vol. v. p. 100, pi. xiv. fig. 43. 

 Cab. A. N. S. No. 20407. 



OBSERVATIONS. 



This shell is remarkable for inhabiting exclusively 

 the small streams, and is common in Greene county, 

 Alabama. It is a variable species, sometimes not 

 easily recognised, and the sexual distinctions are as 

 obvious as in U. siliquoideus. The colour of the in- 

 terior is remarkably inconstant, but a purple ap- 

 proaching to salmon is the most prevailing tint, and 

 the margin is bluish-white. The affinities are U. 

 parvus, Barnes, and V. glans, Lea, but it is much 

 larger than either, has very different beaks, and does 

 not inhabit the same waters with those species. 



