Newell.] 470 [Jan. 18, 



KlONOCERAS ANGULATUM. 



Orthoceras angulatum Wahl. See 20th Kept. State Cab., rev. ed., p. 413. 

 Fragments of this species are from Huntington, Wabash and 

 Delphi, Ind. 



GOMPHOCEBATID^ES. 

 Genus GOMPHOCERAS. 



The genus Gomphoceras of Sowerby includes those nautiloid 

 species with constricted apertures, having straight shells. It dif- 

 fered according to the old classification from the genus Phragmo- 

 ceras, which also had constricted apertures, merely in the straight 

 outline, Phragmoceras having an arcuate shell. 



According to the classification of Prof. Hyatt, Gomphoceras is 

 restricted to those forms having symmetrically constricted T-shaped 

 apertures, including thus the arcuate shells (formerly Phragmo- 

 ceras) as well as the straight shells. 1 



Gomphoceras wabashensis n. sp. 



Compare Gomphoceras rectum Barrande, Syst. Sil.,n, p. 314, pi. 69, figs. 



15-18. 

 Compare Gomphoceras scrinium Hall, 20th Rept. State Cab., N. Y., p. 410. 



Shell is of medium size, straight, characterized by shape of liv- 

 ing chamber and apertures ; the closed chambers and test being 

 unknown. 



The living chamber in general outline is an ovoid with some- 

 what flattened base and a very slight angularity on the ventral 

 side. In a vertical dorsi-ventral section, the slopes of the ventral 

 and dorsal sides are very nearly equal, differing in this respect 

 from the majority of Gompboceratites ; for, in these, as shown by 

 Barrande, the ventral slope is usually greater than the dorsal. Jt 

 thus corresponds exactly to the original definition of Gomphoceras. 

 In horizontal section the chamber is subcircular, with the dorsi- 

 ventral axis longer than the lateral. The chamber is largest at 

 the base decreasing slowly in size on all sides to the area occu- 

 pied by the apertures. The base of the living chamber is strongly 

 convex with no saddles or lobes. 



The T-shaped aperture is situated on the top of the living cham- 

 ber, in a vertical view appearing symmetrically placed in the cen- 



*See Proc. B. S. N. H., 1883, xxir, page 277. 



