No. 2.] BILLINGS — PALEOZOIC FOSSILS. 215 



This species has been found at Bio and St. Simon. 



Fig. 1, 6, representing the transverse section, is not so distinctly 

 flattened on the ventral side as it is in most specimens. 



Collected by T. C. Weston. 



H. Americanos. — Length from twelve to eighteen lines, 

 tapering at the rate of about four lines to the inch. Section 

 triangular, the three sides flat, slightly convex or slightly con- 

 cave, the dorsal and lateral edges either quite sharp or acutely 

 rounded. Lower lip rounded, projecting about two lines in full- 

 grown individuals. Surface finely striated, the striae curving 

 forwards on the ventral sides, and p;issing upwards on the sides 

 at nearly a right angle, curve slightly backwards on the dorsum. 

 In a specimen eighteen lines in length, the width of the aperture 

 is about six lines and the depth about four, the proportions being 

 elightl}' variable. 



The operculum has a very well-defined conical ventral limb, 

 the apex ofw'hich is situated above the centre, or nearer the 

 dorsal than the ventral side. The dorsal limb forms a flat mar- 

 gin, and is so situated that w^hen the operculum is in place, the 

 plane of this flat border must be nearly at right angles to the 

 longitudinal axis of the shell. In an operculum six lines wide, 

 the height of the lower limb to the apex of the cone, is two and 

 a-half lines, and the width of the flat border, which constitutes 

 the dorsal limb, about one line. 



This species occurs at Bic and St. Simon ; also at Troy, N.Y., 

 where it has been found abundantly by Mr. S. W. Ford of that 

 city. It is Theca triangularis of Hail, Pal. N.Y., vol. I., p. 213, 

 18-17. As that name was preoccupied by a species previously 

 described by Col. Portlock, Geol. Rep. on Londonderry, p. 375, 

 pi. 28 A, fig. 3a, 3/->, 3c, 1843, it must be changed. It is a very 

 abundant species, and varies a good deal. 



The Canadian specimens were collected by T. C. Weston. 

 H. MICANS. — This is a lonii' slender cylindrical species, with 

 a nearly circular section. The rate of ttipering is so ."^mnll, that 

 it amounts to scarcely half a line in length of eighteen lines, 

 w^here the width of the tube is from one to two lines. Tiie lar- 

 gest specimen collected is two and a-half lines wide at the larger 

 extremity, and if perfect would be four or five inches in length. 



The operculum does not show distinctly a division into a dor- 

 sal and ventral limb. It is of an ovate form, depth somewhat 

 greater than the width, the nucleus about one-third the depth 



