48 MUSSELS OP CUMBERLAND RIVEE AND TRIBUTARIES. 



the species in its perfection, we have stained horn-colored examples, then deep- 

 brown specimens and specimens with broad distinct rays. Inflated females are likely 

 to have the ridge characteristic of ovata less markedly developed than males; in both 

 sexes, however, there is a tendency for it to appear in all degrees of imperfect develop- 

 ment imtil in some examples it is barely discernible. Indeed in one of our examples 

 it is almost wholly absent, and we have a shell that, with the exception of purely 

 individual features, can not be distinguished from a specimen of L. ventricosa from the 

 upper Mississippi River. 



Judging from the soft parts of a single gravid female examined, the bodies of ventri- 

 cosa and ovata are quite unlike, the mantle flap of ovata showing a peculiar mottling 

 quite different from the markings observed in the other species. 



The variously modified forms of ovata are not only more abundant, but also more 

 widely distributed than the type form. Just below Cumberland Falls most of the 

 shells of this species are of medium size or smaller, nearly all are smoky brown, and 

 several are well-rayed. At Indian Creek Bar brown and few-rayed individuals occur 

 along with the typical form. At Goodall Island we found one with numerous distinct 

 rays. 



The shells of the Rock Castle River are different from the others and can be told 

 almost at a glance. They are dark brown, longer and heavier than those of the other 

 streams and have the posterior ridge rather low; ovata takes nearly the same place in 

 the Cumberland that ventricosa does in the upper Mississippi. 



We have always found ovata considerably inferior to ventricosa as a button shell, 

 being thinner, smaller, and more brittle. The Rock Castle River ovata could possibly 

 be used for buttons, but would furnish rather poor material. In the Cumberland the 

 orata is a rather valueless shell. 



Call's experience with ovata is different. He says it is "one of the largest that are 

 found in American waters; * * * it also attains a much greater size than Barnes's 

 form (ventricosa).'' This may be perfectly true for some rivers, as shelLs vary greatly 

 in size and thickness in different streams. 



11. Lampsilis multiradiata (Lea). 



Rather rare in the main river and found almost entirely in its upper portion. 

 Occurs typically in small, clear streams and often in lakes. It is more common in 

 the tributaries than in the main river. The specimens from both forks of Stones River 

 are beautiful shells, typical in form, not much eroded, and with a clear, white nacre. 

 The specimens from Rock Castle River, Big South Fork, and the main stream depart 

 more or less from the typical form, being unusually elongate and sharp-pointed posteri- 

 orly, rather thin, considerably eroded, and more or less stained or diseased in the 

 Bjfecre or in the teeth. On comparing the Red and Stones River shells with the others, 

 a marked difference was noted in the cardinal teeth. In these typical specimens 

 the large posterior cusp of the right valve pointed more or less anteriorly, while in the 

 Rock Castle River specimens and most of the others it pointed more or less poste- 

 riorly. A few shells with intermediate characters in this respect were found, however, 



12. Lampsilis ligamentina (Lamarck). Mucket. 



This species is represented in the Cumberland chiefly by the southern mucket, 

 Lampsilis ligamentina gihha Simpson, which differs from the typical form in being 

 shorter and more compressed. The two forms grade into each other so impercep- 

 tibly that it is impossible to find the point of separation between them. In the 

 lower part of the river it approaches more nearly the typical form. 



The shell of the subspecies often has the epidermis more highly polished than in 

 the type form, the nacre has more luster, and the valves are flatter and more uniform 

 in thickness. The shells are therefore superior to those of the common mucket for 

 manufacturing purposes and are sought after by shell buyers. Like the other forms 

 of this genus this mucket carries its young in the gills through the winter. The 



