EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 99 



erby. That, however, is a little and deeply sulcate species from the Tilestones. 

 The three varieties of this species described by the Sandbergers from the 

 Devonic are independent species departing widely from B. trisulcatus 

 and doubtless representing distinct genera. One of them, var. tumidus, 

 common in the Spiriferensandstein, is broad and has shallow sulci far at 

 the side, a convex back and apparently no slit band; var. acutus is a 

 Tropidodiscus ; B. coutinhoanus Hartt & Rathbun, from the Erere" 

 Middle Devonic (Brazil) is a Bucaniella with highly convex dorsum and 

 shallow lateral sulci, while Plectonotus ? salteri is a species from 

 Maecuni, likewise with shallow furrows. We have only Plectonotus 

 d e r b y i left as a species characterized by its deep sulci, which are not far 

 to the side, and flat backed dorsum. 



Locality. The Burnt lands 2 miles west of Presque Isle stream, in 

 sandstone. Not observed in the shales. 



Somewhat similar shells occur at Edmunds Hill but they are not in our 

 judgment of the same species, differing therefrom as Bucaniella cou- 

 tinhoana differs from the foregoing. The sulci are more shallow and 

 lateral ; the dorsum is broad and convex. We hesitate therefore to 

 associate them under the same name. 



Tropidodiscus obex Clarke 



Plate 22, figures 27-30 



Tropidodiscus obex Clarke. N. Y. State Mus. Bui. 107. 1907. p. 193 



This is a species of unusual interest in that it represents the only known 

 member of Meek's genus Tropidodiscus, save the type T. curvilineatus 

 (Conrad) from the Onondaga limestone of New York. The Maine shell 

 is smaller than that, very sharply keeled, narrowly umbilicated, with the 

 outward slope of the whorls direct and without evidence of revolving sulci, 

 the inner slope being vertical. The surface is crossed by fine concentric 

 growth lines bending sharply back to the keel. In Tropidocyclus 

 (de Koninck, emend. Clarke) the closely appressed shell still carries pro- 

 nounced revolving furrows, and the slit band, though present, may be 

 obscured by overgrowth or thickening of the shell. 



Locality. Edmunds Hill. 



Coelidium tenue Clarke 



Plate 23. figures 8-10 

 See p. 23 



Coelidium tenue Clarke. N. Y. State Mus. Bui. 107. 1907. p.190 



This is an elongate, turriculate and slender shell with sharply keeled 

 whorls margined by a simple slit band to which the surface slopes in an 

 almost direct plane without either convex or concave curvature, the surface 



