Maryland Geological Survey 307 



Class CEPHALOPODA 



Subclass TETRABRANCHIATA 



Order NAUTILOIDEA 



Suborder ORTHOCHOANITES 



Family ORTHOCERATIDAE 



Genus ORTHOCERAS Breynius 



Orthoceras bebryx Hall ( ?) 

 Plate XXXVIII, Figs. 10, 11 



Orthoceras tehryx Hall 1876, 111. Dev. Fossils: Cephalopoda. Explanation 



pi. xxxix, figs. 1, 2. 

 Orthoceras hehryx Hall, 1879, Pal. N. Y., vol. v, pt. ii, p. 275, pi. xxxviii, 



fig. 10; pi. xxxix, fig. 2; pi. Ixxxiii, fig. 14; pi. Ixxxiv, figs. 11, 12. 

 Orthoceras bebryx Clarke, 1903, N. Y. State Mus., Bull. 65, p. 618. 



Description. — Shell robust, straight, regularly enlarging from the apex; 

 transverse section, allowing for the degree of compression, suhcircular. 

 Living chamber not fully observed; air-chambers regular, increasing in 

 depth from the apex, and varying in different individuals from six to ten 

 mm. Septa smooth and thin, so far as observed; sutures, in specimens 

 not distorted by compression, straight and horizontal; siphuncle monili- 

 f orm, expanding between the septa, and having a diameter equal to, or two- 

 thirds of, the depth of the air-chambers, the position is probably slightly 

 eccentric. The test has not been preserved but the casts of the interior 

 indicate a transversely lamellose-striate surface. A fragment, embracing 

 a portion of the chamber of habitation and seventeen of the adjacent air- 

 chambers, ha? a length of 220 mm. 



Several fragments of a large Orthoceras occur in the Maryland Col- 

 lection, which probably belong to this species. They are mostly internal 

 impressions, and the one figured shows apparently part of the living 

 chamber and six air-chambers which vary in depth from 6^ to 9 mm. 

 Another specimen shows a large chamber of habitation, which is flattened 

 by crushing; while an external impression of a large specimen which 



