PALEONTOLOGY. . 427 



chamber of habitation. Many species of Orthoceras have been observed, 

 having a raised line, or rather markings, along the dorsal side; but none, 

 so far as I am aware, presenting these evidences of a series of separate 

 openings, which I consider a feature worthy of generic distinction. 



Trematoceras Ohioense. 



Plate VI, figs. 3 and 4. 

 Trematospira Ohioense Whitf., Ann. N. Y. Sci., March, 1882, p. 206. 



Shell of medium size, straight, and somewhat rapidly tapering from below 

 upward; the rate of increase being equal to nearly one-sixth of the increase in 

 length. Septa moderately concave, rather closely arranged; five of the chambers 

 about equaling the diameter of the uppermost of the five counted. Siphon of mod- 

 erate size, and in the specimen used slightly eccentric. The surface of the shell, so 

 far as can be determined from the internal cast, has been smooth. Periorations, or 

 nodes representing them, large and elevated, two to three times as long as wide,, 

 and occurring at every third septum below, and at every second in the upper part 

 of the specimen. 



Formation and Locality. — In limestone of the Upper Helderberg 

 group, at Smith and Price's quarry, near Columbus Ohio. The discovery 

 and preservation of this peculiar specimen are due to the careful observa- 

 tion of Mr. Edward Hyatt, of the State University, at Columbus, Ohio. 



Genus GOMPHOCERAS Sowerby. 



Gomphoceras Hyatti. 



Plate IV, fig. 1, and Plate I, fig 1. 

 Gomphoceras Hyatti Whitf., Ann. N. Y. Acad. Sci., March, 1882, p. 206. 



Shell large and robust, slightly arcuate throughout, but more strongly curved 

 below than in the upper part ; somewhat rapidly expanding from below upward to 

 near the middle of the outer chamber, where it is suddenly contracted to the aper- 

 ture, and on the lateral margins again slightly expanding. The rate of increase iu 

 diameter, as compared with the increased length, is about as one and two, when 

 measured on the inside curvature.' Transverse section of the shell obtusely subtrian- 

 gular, flattened or but slightly convex on the inner surface, rounded on the lateral 

 surfaces, and obtusely rounded on the back; the dorso-ventral and lateral diameters 

 are about as four and five, and the triangular form is more perceptible in the earlier 

 stages of growth, owing to the greater convexity of the inner face in the upper 

 portion and on the outer chamber. Outer chamber comparatively short, being about 

 two-thirds as high as wide. Aperture large, irregularly tri-lobed, straight on the 

 inner face, and about four-fifths as wide as the entire width of the shell, and ap- 

 parently about two-thirds as wide in a dorso-ventral direction as laterally. The 

 exact form of the aperture on the outer side cannot be ascertained, owing to the 

 imperfection of the specimen iu this part. Septa moderately concave, very closely 

 arranged in the lower part, but more distinctly disposed above ; the rate of increase 

 in distance somewhat gradual to near the upper portion, where two or three of the 

 septa are slightly more crowded. In the more distant portions, three chambers oc- 

 cupy the space of one inch, but in the lower part of the specimen, where the trans- 

 verse diameter is a little more than one and a half inches, they are less than one- 

 twelfth of an inch apart. Siphuncle of moderate size and sub-centrally situated. 

 Surface of the shell unknown. 



