PLATE XVI. 



Page. 



Fiff. I. Spii.KitnM ? Idahoe.vse Ifti 



1. A specimen consisting mainly of an internal ( ast, witli scime (lortions of tlie shell 

 remaining. 



1 a. An outline to show the convexity of the same. 



Fig. -i. Sph^khium ntjoosiT.M Hii 



■2. A rather small specimen, enlarged two diameters. 

 'Z a. A larger specimen, enlarged two diameters. 



2 6. An outline to show convexity, enlarged two diameters. 



Fig. :?. Unio Haydkni 184 



5. View of left valve. 



3 a. Same view of a larger specimen. 



:i fc. Internal cast, showing an impression of the hinge. 



Fig. 4. Unio helllplicatd.s 165 



4. Left side of one of the larger specimens. 



4 «. Right view of a smaller individual of .same. 



Fig. .">. Unio vetustus Iii 



.""i. A young shell flattened by pressure, with a jiart of the posterior Imiken away. 

 (Original type of the species.) 



5 a. A large specimen, somewhat twisted over by oblique jjressure. so as to hide the beaks. 

 5 &. A dorsal view of same. 



.'■> c. A smaller specimen of same. 



Fig. (!. C YiiEXA (Velohii'INa) Dukkeei U)7 



6. A medium-sized specimen. 



fia. An anterior view of same, showing its unusually deep and well-deliued Inuule. 



(> 6. A larger individual. 



G c. A very gibbous, short variety. 



(id. A dorsal view of same, showing the deep posti^rioi dorsal (•onoavity. 



() c. A separate left valve, showing hinge. 



fi/. A small, depressed variety, or possibly a distinct species. 



ti(/. An internal east, showing muscular impression, and the slightly sinuous pallial line. 



