60 MXJSSELS OF CUMBERLAND EIVER AND TEIBUTARIES. 



Q. lachrymosa and is of little commercial value. We found gravid examples below 

 Kuttawa May 17 and at the foot of Dover Island May 29. All four gills ser\'e aa 

 marsupia and are thick and pad-like. 



67. Quadrula pustulosa (Lea). Warty -back. 



Common throughout the entire length of the river. Our shells exhibit a marked 

 uniformity in general appearance, being rather inflated with only a moderate num- 

 ber of low tubercles. A few shells found a mile below Cumberland Falls are almost 

 entirely smooth. With the exception of the Half Pone Bar specimens most of the 

 '■hells have a cloth-like epidermis. 



The warty-backs of the Cumberland are as a rule rather undersized, and their 

 inflated. form is something of a disadvantage, so that they are not as valuable as in 

 some other streams. 



68. Quadrula cooperiana (Lea). Cumberland pigtoe. 



Not rare in the Cumberland. The proportions of the shell vary considerably, some 

 being higher than long and others longer than high. The older examples are gen- 

 erally more elongate than the younger. The shells also vary somewhat as regards 

 degree of inflation. One of the young shells has the epidermis faintly rayed, the 

 others are eradiate. Three of the shells have the epiderlnis polished and shining; 

 in the others it is dull. The nacre is sometimes a pale suffused pink 'udthin the 

 pallial line, but in the majority of cases it is pure white. This is regarded as a very 

 fair button shell. In appearance it lies intermediate between pustulosa and grani. 

 /era. From granifera it can always be distinguished by the color of its nacre. It is 

 usually longer and flatter than pustulosa, and there are peculiarities of epidermis, 

 disposition of pustules, and shape of teetn that taken together help to separate them. 

 They can always be separated if in the flesh, as cooperiana always has an orange- 

 yellow flesh. The ova which fill the gills are bright yellow. 



We found only two examples gravid, early in June. The developing ova were 

 borne in the outer gills and gave it a sulphur-yellow color. 



Dr. Ortmann removes this species from the genus Quadrula and places it in Pleu- 

 robema; he remarks that it is closely related to P. sesopus. We are rather favorably 

 inclined to this view, but in view of the fact that these two genera need a thorough 

 revision and may possibly run into each other we prefer at present to leave it where 

 Simpson placed it, among shells that it strongly resembles. 



Q9. Quadrula rubignosa (Lea). Wabash pigtoe. 



This species was found nowhere except in the East Fork of Stones River at Walter- 

 hill, Tenn. The shells show very little difference in general appearance, except 

 that in the smallest the posterior ridg? is poorly defined, and one of the medium- 

 sized examples is somewhat more rounded, and has a lower posterior ridge. Large 

 examples of this species make a moderately good button shell. 



70. Quadrula undata (Barnes). Pigtoe. 



This, as Bryant Walker has shown, " is the proper name for the Quadrula trigona 

 (Lea) of Simpson's Synopsis. Ortmann b regards it as a subspecies of Q. rubiginosa. 

 Though we have observed great variation in this shell, we have never seen any transi- 

 tion forms between the two species. It is rare in the Cumberland and the shells 

 are rather small, measuring about 45 mm. long, 43 mm. high, and 25.7 mm. in diameter. 

 The epidermis is clothlike and finely striate. The flesh is orange, in which respect 

 it approaches rubiginosa. 



An example procured at Linton, Ky., had a dorsal baroque, and the mantle con- 

 tained 4 marginal distomid cysts, a parasite which is especially frequent in this species. 



6 Nautilus, vol. x.xiu, no. 9, Feb., 1910, p. 116. 



