[WILLIAMS] FOSSIL FAUNAS OF THE ST. HELEN'S BRECCIAS 219 



is a not infrequent character, but it is nrtt universal. This character 

 is described as " a dependable feature in determining the young forms 

 of the shell with which the rocks abound/' by J. M. Clarke, in describing 

 the Chonetes canadensis from the Grande Grève limestone of Gaspé 

 (p. 20 ), which .remark suggests probability of specific identity of the 

 species from the two localities. A specimen from St. Helen's shows 11 

 lineations in the distance of two millimeters along the front edge of a 

 specimen about 10 mm. long; specimens from Chapman sandstone of 

 same size show from 10 to 12 lineations. Specimens of CJionetes liud- 

 sonicwi inetafype gaspensis, Clarke, of about the same size show 6 linea- 

 tions in the space of two millimeters at corresponding distance from the 

 beak. Specimens of Chonetes coronata from the Hamilton (from locality 

 1066 A; U.S.G.S.) show 'scarcely 5 in the same distance. Both speci- 

 mens showing the exterior of the pedicle valve are exfoliated and only 

 the inner layers of the shell are evident, but along the middle there is 

 a slight elevation. Among the specimens from the Chapman sandstone 

 many vshow the median line, but some specimens in which the surface is 

 present do not show it. While it is possible that the large forms called 

 CJionetes canadensis, Billings, are identical with the small broad forms 

 with strong median longitudinal lines on ventral valve called by us 

 Chonetes striatissirmis. the uniformly small size of the latter species in 

 the t\T5ical localities is warrant for continuing the use of its name. The 

 presence of this type of finely lineato, flat, large sized Chonetes is in 

 itself strongly suggestive of a Lower Devonian horizon for both North 

 America and Europe, and the association of the two types points the 

 same way. 



10. Camarotœchia sp. indet. 



A fragment showing a prominent elevation of the fold at the front 

 with a few faint plications on the sides, somewhat resembling Eatonia, is 

 referred to the genus Camarotœchia with doubt; its specific and even 

 generic characters are indistinct. It is of no value in determining the 

 horizon. 



11. Rhynchonella (Uncinulus) mutahilis, Hall. 



A single small specimen presents the form and plications of this 

 'species. Its dimensions are 13 mm. long by 9.8 mm. wide; the thickness 

 of the two valves together is 11.4 mm. It shows about 12 plications 

 from the middle outwards. Another specimen (fragment) belonging to 

 a larger shell, probably 20 mm. long, is also referred to the same species. 

 This type of Ehynchonella bespeaks for American sections a Lower 

 Devonian horizon. No such species is reported from the middle De- 



