Newell.] 476 [Jan. 18, 



than the dorsi-ventral diameter at the last septum ; this length 

 also about equals the dorsi-ventral diameter at the aperture. The 

 greatest lateral diameter of the shell is from one-half to one-third 

 these latter measurements. The sides of the shell are quite flat 

 over the central area. At the aperture the side flaps turn in rap- 

 idly, contracting the middle of the aperture to a narrow channel. 



The ventral opening of the aperture is prolonged forward into 

 an oval tube, with its greatest diameter coinciding with the length 

 of the shell. The dorsal aperture is destroyed in all the speci- 

 mens. 



The air chambers are regular and deeply concave. The sutures 

 form ventral and dorsal saddles and broad lateral lobes. 



The siphon is comparatively small, moniliform, situated close to 

 the ventral side. Test and surface unknown. 



The type specimen figured above measures : — dorsi-ventral diam- 

 eter of the smallest air chamber 52 mm., dorsi-ventral diameter of 

 last septum 105 mm., dorsi-ventral diameter of the region of the 

 aperture 140 mm. This species is distinguished from G. ellipti- 

 cum by the outer chamber being higher than wide, and in having a 

 more decided curvature. 



Comparing G. angustum and G. ellipticum with G. linearis, we 

 have a series in size, comparative height and length of living cham- 

 ber, and concavity of the septa. G. linearis is the smallest, the 

 living chamber is relatively lowest and the sutures are straight, 

 G. ellipticum stands intermediate in these respects and G. angus- 

 tum is largest, has greatest relative vertical height of living cham- 

 ber, and greatest convexity of septa. 



Locality. — Wabash City, Indiana. 



GOMPHOCERAS PROJECTUM n. Sp. 



Compare Gomphoceras (Phragmoceras) parvum H. & "W., Pal. Ohio, n, p. 



151, pi. 8, fig. 10. 

 Compare Gomphoceras (Phragmoceras') nestor Hall, 20th Kept. State Cab. 



N. Y., rev. ed., p. 405. 

 Compare Gomphoceras (Phragmoceras) labiosumBsa-rande, Syst. Sil., n, p. 

 218, pi. 50. 

 Shell small, flattened, and strongly arcuate ; in transverse sec- 

 tion elliptical. 



The living chamber in cross section is narrowly ovoid. The dorsi- 

 ventral diameter increases rapidly upward toward the apertures 

 but the lateral diameter increases slowly. The ventral side is 



