N0.2.J SNAILS OF THE GENUS 10— ADAMS. 57 



in some cases it will be impossible by inspection alone to determine the true character of the 

 shell, but this may be learned by breaking away the overlying whorls. And in case no young 

 shells are found, it is at least sometimes possible to thus restore the lacking youthful stages. 



The apices show that adult spinose shells may be smooth or corrugated in a late stage in 

 class 1 ; and an examination of adult shells in group 9, from Chnchport, also agrees with the broken 

 shells, and shows two kinds of apices at the class 2 stage — one smooth, plate 37, figures 23, 28, 

 29, 31, and 32, and the other corrugated, as in figures 1, 15, 19, and 20. One relatively smooth 

 shell, figure 33, shows spines and by its spines suggests contamination or inversion. 



Below Clinchport, in the Chnch, very few immature shells were found, and some belonging 

 to class 3 were found in lot 17. These show, plate 3, figures 43-44, an undulate tendency on 

 the upper whorls at the class 2 stage, and the last whorl is strongly spinose. A shell in lot 18 

 (No. 48) is in the class 2 stage, and it was spinose from the class 1 stage onward. Two other 

 individuals have evidently had the same history (Nos. 47, 49) . Two shells in the class 3 stage 

 from lot 21 have relatively smooth apical whorls, but are undulate. One continued faint 

 undulations after the class 1 stage, while the second passed the class 2 as a smooth shell. Both 

 are spinose on the remainder of the shell. Lot 20 contains two shells of the class 3 stage, with 

 apices and spines on the last and the whole or a part of the preceding whorl. Lot 32 contains 

 one shell in the class 2 stage. It was minutely spinose from the class 1 stage, and remained 

 spinose. The other shell is in the class 3 stage, and has two whorls with spines. 



c. Holston River System. — ^Very yoxmg shells are rarely found in the upper Holston. The 

 apices of the shells in group 12, from SaltviUe, at the class 2 stage, were smooth or possibly 

 corrugated, plate 40. The few immature shells are mainly of class 3. The two individuals 

 of class 2 are smooth, but at the class 1 stage both (Nos. 166, 167) had undulations. As class 

 3 stage develops, all degrees up to a distinctly undulate condition are produced. Even among 

 the adult shells perfectly smooth individuals are the exception. In lot 1 1 1 , from Holston Bridge, 

 near Big Moccasin Gap, there are two shells in the class 3 stage. The apex of one at the class 

 1 stage was smooth, but showed minute undulations; after this stage it became undulate. The 

 other shell was strongly undulate or truly spinose from the start. From the South Fork at Bluff 

 City, lot 94, classes 2 and 3 are represented among these by a few individuals, plate 4, figures 

 1-6, 8-9. These shells are smooth or show irregular transverse undulations or corrugations, 

 as is also clearly shown on the apical whorls of some of the older shells, plate 41. A very few 

 individuals remain smooth through the class 3 stage, plate 4, figure 10, and others to maturity. 

 In a few of the adults the body whorls are practically smooth, even though some of the younger 

 whorls are undulate, plate 41, figure 1. In several old individuals the latest growth, only about 

 one-fourth of a whorl, is free from undulations or nearly so. The early development of undula- 

 tions on these shells is characteristic of the South Fork shells. The undulations on the apical 

 whorls recall somewhat similar ones found upon class 1 shells in lot 51 from Clinch River, plate 

 3, figures 35 and 36, but the Chnch River and Bluff City sheUs develop with age very different 

 kinds of undulations or spines. 



Four specimens of about class 2 and class 3 stage were found at Curry Ford, lot 86. All 

 are spinose on the body whorl, as shown in plate 3, figures 45-48. In lot 85, from Hord Ford, 

 there are two smooth shells of class 2, plate 3, figures 49-50. The shells from Chissolms Ford, 

 lots 97 and 98 (group 15), are quite remarkable for immature shells, plate 3, figures 51-67, also 

 plate 43. No individuals were found belonging to classes 1 and 2, but class 3 is represented by 

 small and large individuals, the large ones more abundantly. In some of these shells the upper 

 edge of the whorls tend to overlap to such a degree as to obscure the spinosity of the earher whorls. 

 At the class 2 stage some individuals show a marked tendency to be spinose; and later, as the 

 shells mature, to reduce or eliminate these spines, as shown on the plate. There is a great va- 

 riation in the degree of completeness of this loss of spines. In no other locality is this tendency 

 so well marked and complete. Class 3 at this locality contains both smooth and spinose shells. 

 The occurrence of such large smooth {fluvialis ?) shells so far from the headwaters is particu- 

 larly remarkable. 



