58 MEMOIRS NATIONAL ACADEMY OF SCIENCES. [vol.xii. 



The young shells of group 16, lots 87 and 88, plate 4, figures 21-34, from near Rogersville, 

 are similar to those from Chissolms Ford, but include a smaller proportion of shells which are 

 spiny at the class 2 or class 3 stage and become smooth later. Young shells at the class 2 or 

 3 stage are quite variable on the last whorl; smooth, transversely undulate, carinate, and nodu- 

 lose. Many of the class 3 shells are smooth or approximately so at the class 2 stage. At the 

 class 1 stage some of these shells were smooth, as figure 22, while others, as figure 23, were spinose. 

 The class 1 shells of lot 88, plate 4, figures 14-20, are smooth, carinated, and with traces of spines. 



A good series of shells from Rogersville, belonging to the Mrs. George Andrews' collection, 

 contains a number of immature shells. The yoimgest are in the class 2 group, and smooth with 

 indications of corrugations and carination. The young of the class 3 stage are of two kinds. 

 One kind would be considered smooth, but it shows faint and irregular imdulations on the 

 apices and even nodules or spines on the latest formed part of the whorl. The other kind has 

 similar apices, but at the class 2 and almost the class 3 stage it becomes very spinose. Inver- 

 sion is frequent in this series, and there is a considerable amovmt of overlapping of the whorls 

 upon the spines. 



In lot 90, from Cobb Ford, plate 4, figures 35^7; plate 5, figures 1-5; and plate 45, imma- 

 ture shells are particularly abundant. A few belong to class 2, but class 3 is very abundant. 

 The apical whorls of the class 3 shells, corresponding to class 2, are either smooth, plate 4, 

 figure 43, or spinose, as on plate 5, figure 2. Some individuals in class 2 are nodulose, as plate 

 4, figure 35, while others reach class 3 before nodules or spines are developed, as figure 44. The 

 variations in classes 2 and 3 are well shown on the plates. Among these shells are three which 

 are nearly smooth, figures 42-44, but these when older might have developed large spines, 

 as did one individual of this lot, plate 5, figure 4. 



From about 13 nules farther downstream, at Holston Station, north of MorristoTVTi, lot 96 

 (group 18) is found to contain shells which are much more mature and larger than those in lot 

 90. The immature shells, except one individual of class 1, plate 5, figure 12, belong to classes 

 2 and 3. Only a few belong to class 2. The class 1 individual has seven whorls. The five 

 apical, evidently embryonic, whorls appear nearly smooth, and no carina can be recognized. 

 The undulations on the last two whorls are distinct and numerous but not strongly carinated 

 as are the young of lot 104 from the NoHchucky, to be discussed later. This shell is 10 mm. 

 long and 6 mm. in diameter, and has an aperture of 6.8 mm. in length. The spinose class 2 indi- 

 viduals are distinctly corrugated at the class 1 stage, and the corrugations develop directly into 

 distinct spines. The smooth individual of this class was corrugate at the class 1 stage, then 

 became smooth, and on the last formed part of the shell made two incipient nodules. 



In lot 91, from Strawberry Plains, Tenn., the few shells of class 3 show apical whorls smooth 

 at the class 2 stage, but with distinct spines on the body whorl as in plate 5, figures 6-8. This 

 is one type of young which is also very characteristic of the Tennessee River, as will be shown 

 later. Other individuals show the transition to the distinctly spinose young at about the class 

 2 stage, plate 5, figures 9-10, and spinose at class 1 stage, figure 11. Lot 123, from Dopes Bar, 

 plate 5, figures 13-14,contains two young shells which are smooth at practically the class 2 stage, 

 but contain large spines on the body whorls; others remained smooth through the class 3 stage, 

 and then became spinose. Another shell, lot 203, from near the mouth of the Holston, is in 

 class 3 and is also smooth on all but the body whorl, plate 5, figure 15. The shells of the lower 

 Holston, as in the lower Powell and Clinch, show both smooth and spinose young shells. 



d. NolichucJcy and French Broad Rivers. — From the upper waters of the Nohchucky no live 

 shells were secured; and the few dead shells were found on the sites of ancient Indian camps. 

 These shells are of importance because they show clearly that the young shells are spiny, Hke 

 the adults. Small shells of about classes 2 and 3 occurred in lot 119 from Conkhng, Tenn,, 

 plate 47, figures 14-16; in lot 118 from BroylesvUle, Tenn., a few individuals of class 2 and a few 

 of cla^s 3, and some abo in lot 117 from Limestone, Tenn. These observations on the young 

 hells corroborate the evidence preserved upon the apical portions of older shells, and show 

 clearly that they are very spiny and that only shells which are spinose when young occur in the 



