PALEONTOLOGY OF NEW YORK. 



tures, but the septa are a little more frequent, and none of the specimens 

 referred to that species have shown any indication of the ventral carina on the 

 cast of the interior. 



Formation and locality. In the shales of the Hamilton group at Monteith's 

 Point, Canandaigua lake, N. Y. 



Orthoceras emaceratcm. 



PLATKS XXXIX, FIG. 4; LXXXV, FIG. 16. 



Orthoceras emaceratum. Hall. Fifteenth Rep. N. V. State Cab. Nat. Hist., p. 170, pi. 8, fig. 7. 18(52. 



" •' Illustrations of Devonian Fossils : Cephalopoda. Explanation of plate 39, 



fig. 4. 1876. 



Shell straight, slender, gradually enlarging from the apex. Transverse section 

 subcircular. Apical angle 4J°. Initial point unknown. 



Chamber of habitation not observed. Air-chambers regular, gradually 

 increasing in depth toward the grand chamber, varying from six to nine mm. 

 in the length of eigbty mm. 



Septa and siphuncle unknown. Sutures straight and horizontal. 



The test has not been preserved, but some specimens show traces of trans- 

 verse striae. 



The internal mould is smooth, with the sutures but little impressed. 



One fragment, embracing twenty air-chambers, has a length of 125 mm., 

 with a diameter at the smaller extremity of ten mm. Another portion of a 

 larger individual has twelve chambers in the length of ninety mm. 



All the specimens of this species are from the soft shales in the western part 

 of the State. They are usually much flattened and broken from compression, 

 and the test has been destroyed. The distinguishing characters are the depth 

 of the chambers, compared with the diameter of the tube, and the small apical 

 angle. In its general aspect and association it is similar to 0. aulax ; but the 

 marked surface ornaments on the latter species, which are also shown on the 

 internal mould, are characteristic. 



Formation and locality. In the soft shales of the Hamilton group, in Genesee 

 and Erie counties, N. Y. 



