54 MUSSELS OF CUMBERLAND RIVER AND TRIBUTARIES. 



anteriorly, but the greater number are too deeply stained for the rays to show. In 

 the living animal the mantle is prettily rayed. 



The shape, size, and solidity of the shell of this species make it suitable for the 

 manufacture of buttons, but unfortunately it is too brittle and hard, resembling 

 Pleurobema seso-pus in this respect. About one-third of the shell, moreover (the tip 

 part), is of a pink tinge, which runs entirely through the shell, making it of no value. 



42. Dromus caperatus (Lea). Fan mussel. 



The examples of Dromus obtained in the Big South Fork of the Cumberland differ 

 from those found in the main river by being considerably flatter, with the hump on 

 the disk less pronounced or nearly absent. These flattened shells represent the species 

 caperatus (Lea). Our series indicate that the two forms run together. In young 

 specimens, before the step-off is formed, it is doubtful if dromas and caperatus could 

 be distinguished. 



From what has been said concerning the relationship between this and the pre- 

 ceding species it may be readily inferred that this species also, from a commercial 

 standpoint, is valueless. 



43. Strophitus edentulus (Lea). Squaw-foot. 



We found only a few examples of this species. It has a fragile shell, which, disin- 

 tegrates quickly and is probably more common than our small collection would indi- 

 cate. Mr. Boepple found it at Pineville, the highest point at which the river was 

 examined. It is a species which occurs in all sorts of situations — in both small and 

 large streams and in lakes. Two of our specimens have a pink-purple nacre; in the 

 others it is of a yellowish cast. The species is of no value on account of its thin, brittle 

 shell. It is exceedingly variable, and presents many puzzling forms. According to 

 Mr. Bryant Walker our specimens represent the form ahaefferiana Lea. 



44. Anodonta imbecilUs (Say) . 



The distribution of this fragile, beautiful species is almost identical with that of 

 A. grandis. Of the two found in Haynes Lake one was gravid (Sept. 3). The glo- 

 chidia are rather large, cliestnut-shaped in outline, brown, and fill the entire outer 

 gills. The species remains gravid through the winter. The Haynes Lake sheila 

 contained several Atax apiece. 



45. Anodonta grandis (Say) . 



This species was not found in the main river. In general, conditions throughout 

 the whole Cumberland system are not favorable to its development. The small 

 tributaries are too swift and rocky, and the Cumberland itself is lacking in the quiet, 

 muddy sloughs in which A. grandis can thrive. The only river examples we found 

 were in the Stones River, a few in the East Fork nearWalterhill, Tenn., and several 

 in the West Fork near Murfreesboro. At the last-mentioned place it had apparently 

 once been abundant in the vicinity of the railroad bridge, where it had thriven in the 

 mud of the deep, quiet pools among the water-willows. A number of shells, recently 

 killed by pearlers, were lying on the bank. These were large, heavy shells, unusually 

 thick for the species, and varied considerably in shape, some of them being markedly 

 elongate. 



In Haynes Lake, a shallow, muddy pond below Clarksville, Anodonta grandis was 

 fairly abundant, and about 30 examples were secured. These were more shapely, 

 of a larger size than those from Stones River, and much thinner. They are indeed 

 the largest and finest examples of the species we have ever seen and represent the 

 form gigantea Lea. The largest example measured 201.3 mm. long, 112.5 mm. high., 

 and 82.3 mm. in diameter. These shells are peculiar in having two distinct colors of 

 nacre, about half of them being dark purple, while the other half are a beautiful, 

 lustrous, creamy white. The reason for this difference is not apparent; parasites are 

 almost entirely absent. 



