INDEX OF GENERA AND SPECIES. 



243 



TYPHIS, 82. 



Typhis antiquus, 82. 



UNICARDIUM, 50. 



? Unicardium gibbosum, 50. 

 UNIO, 182. 



Unio penultimus, 182. 



VENUS, 161. 



Venus lenticularis, 162. 

 tetrahedra, 163. 



Yenus varians, 161. 

 Yeatchii, 162. 



VOLUTALITHES, 102. 



Volutalithes Navarroensis, 

 102. 



WHITNEYA, 103. 



Whitneya ficus, 104. 



YOLDIA, 216. 



Yoldia nasuta, 216. 



