58 •!. y. MATTHEW: ILLUSTEATIONS OF 



Sculplure. The concentric ridges are about as numeroiis as in the j)rececliug species, 

 but the radiating- striœ are more distinct and more widely spread, there being about four 

 on the dorsal third and about five indistinct striœ on the lateral third. 



More numerous examples may show that this is a variety of the preceding species, 

 but at present it appears to be distinct ; although much smaller it has as many concentric 

 ridges as <S. ccncenlrica.. 



Length, to the middle of the aperture, IJmm. Width of aperture, 2 mm. 



Horizon, and Locality. In the dark grey shales of Div. l.r, at Porter's Brook, St. Martin's. 

 Rare. 



Stenotheca nasitta, n. sp. (Plate VI. Fig. 13.) 



Subtriangiilar, with deeply concave posterior slope. Apex not known, but probably 

 elevated. Dorsal and A^entral slopes of about equal length ; the dorsal convex, the ventral 

 prodviced at the aperture into a projecting point. Base of the shell strongly arched. 



As preserved in the shale there is a raised rib both on the dorsal and ventral slope, 

 that on the dorsal being the wdder ; there are also on the sides of the shell about four 

 rounded concentric ridges, with sharp projecting edges. 



Sculpture. The surface is smooth or nearly so. except on the dorsal rib, where a num- 

 ber of faint striae, concentric with the apex, are discernable with a lens. 



Length, exclusiA'e of the deficient (broken ?) apex, 1.? mm. Width, 3 J mm. 



Horizon and Locality. In the fine grey shales of Div. \.c, at Hanford Brook, St. Martin's. 

 Rare. 



Stenotheca tuiangulaeis, n. sp. (Plate VI. Figs. 15 and 1.5a.) 



Outline triangular, and apex projecting. Dorsal slope about one half longer than 

 the ventral ; the former slightly conA'ex, the latter moderately concave ; the base of the 

 shell is straight in the middle two thirds, but deflected upward at the extremities. The 

 apex is long, cylindrical, and pointed backward, and a narrow, smooth area extends from 

 it half way down the ventral slope. 



Hcidpture. The surface is diversified by about six or more distinct, strongly elevated, 

 concentric ridges, which are abruptly turned upward at the dorsal margin, presenting a 

 series of tubercular elevations along the dorsal line ; the outer (lower) ridges are also bent 

 iipward at the ventral margin. Each concentric ridge is traversed lengthwise by about 

 six stritc, which are visible only with a lens. The mould of the shell exhibits a series of 

 cavities behind the tubercles on the dorsal line. 



The form of this shell is not unlike that of S. cornucopia, Hicks, (referred to above), but 

 it is distinct in its less numerous concentric ridges. 



Length, 3J mm. Width of aperture, 5 mm. 



Horizon and Locality. In the fine grey shales of Div. l.r at Portland, and at the same 

 horizon on Hanford Brook, St. Martin's. Infrequent. 



In the measures of Div. l.c there is a larger mollusc which, though agreeing with the 

 typical Stenothecœ in most respects, has some important points of diiference. This species 

 exhibits relations with Metoptoma (?) rugosa of the Trenton formation. It is much larger 



