46 MUSSELS OF CUMBERLAND EIVER AND TEIBUTAEIES. 



occurring in moderate-sized, clear streams with a rocky bottom, avoiding the smaller 

 tributaries. 



3. Truncilla arcseformis (Lea). 



Rare; only one example obtained. This was procured in the Big South Fork 2 

 miles above Burnside, Ky., and is rather peculiar in shape. 



4. Truncilla sulcata (Lea). Pewee, cat's-claw. 



Although this species seems to be pretty well distributed along a considerable 

 stretch of the river, we obtained only occasional examples here and there along shore. 

 Mr. Boepple found one in Caney Fork. It can probably be procured in larger num- 

 bers during low water. It is common enough to be pretty well known to the clammers, 

 who call it "pewee" on account of its small size, or cat's-claw" because of the 

 peculiar clawlike structures on the marsupial expansion of the shell of the female. 



5. Truncilla haysiana Lea. 



Our collection of this species is rather small, but it is probably more common than 

 the collection would indicate, as it is too small to bite on the crowfoot hook and is 

 easily overlooked. Most of the examples collected had been killed and cleaned by 

 muskrats. It is one of the handsomest of the Truncillas on account of its beautifully 

 polished epidermis, and it has an unusually thick and solid shell for the genus. It is, 

 however, too small for manufacturing purposes. 



6. Truncilla capsxformis (Lea). 



Fairly abundant in the Big South Fork, where nearly all the specimens had been 

 killed by muskrats; in the main river we found it sparingly. Our shells are pretty 

 badly eroded, very thin and brittle, with the marsupial expansion colored a dark 

 green. The species is of no value for manufacturing purposes, being too small and 

 thin. 



7. Truncilla florentina (Lea). 



Rare; the only specimen obtained was the dead shell of an old and very inflated 

 female at Half Pone bar. In the autumn of 1910 Mr. Boepple found a specimen at 

 Indian Creek bar. During low water probably many more could be obtained. 



8. Truncilla walkeri, new species. (See fig. 1, frontispiece.) 



A fine, large Truncilla with a honey-yellow epidermis and numerous capillary rays. 

 Shell rather thin, elliptical in outline, much inflated in the females, only moderately 

 in the males. Anterior margin projecting and evenly rounded, ventral margin 

 strongly convex in the larger males, much less so in the females and smaller males; 

 posterior margin oblique, but usually well rounded in both sexes; dorsal margin 

 comparatively long, straight, or slightly curved. Umbones narrow and flattened. 

 Anterior, lateral, and posterior slopes all well rounded; umboidal ridge flattened and 

 indistinct, especially in the females. In front of this ridge the males have a broad 

 and shallow sulcus; in the females the marsupial expansion is very pronounced, and 

 is usually limited anteriorly and posteriorly by a deep and narrow sulcus. It is 

 somewhat like that of caps8p/ormis, but is considerably swollen, especially in the 

 larger females, instead of being flattened, and does not project as strongly. Lines of 

 growth smooth, distinct, and close together. Ligament long, thin, and light brown. 



Interior: Pseudo cardinals large and thick, rather blunt and only slightly serrate or 

 smooth; laterals long, high, thick, and slightly curved; anterior adductor scar slightly 

 longer than wide, squarely truncated posteriorly; posterior scar large, deeply impressed, 

 and squarely truncated anteriorly much as in brevidens; pallial impression fairly dis- 

 tinct, nacre milky white, thinner and quite iridescent posteriorly. 



This species was quite abundant just below the ford of the East Fork of Stones 

 River near Walterville, Tenn. We found here 140 shells, most of them on shore and 

 recently killed by muskrats, and 1 or 2 living mussels. The smallest specimen (male) 



