206 PALAEONTOLOGY OF NEW-YORK. 



Fig. 1 a. A young specimen, with the shell partially exfoliated ; a few of the septa being indistinctly 

 visible. 



Fig. \ b. A. fragment, showing the shell in a considerable degree of preservation. 



Fig. 1 c. A portion of the surface of the last enlarged, showing the flexuous character of the striae. 



Fig. \ d. A large specimen, preserving but indistinctly the strice. About twenty of the chambers are 

 preserved, as well as a large part of the outer chamber. This specimen shows a small septate 

 tube within the open extremity, but it is probably accidentally present. 



Position and locality. This species occurs in the higher part of the Trenton limestone at 

 Middleville. 



17. 2. ORTHOCERAS LAQUEATUM. 



Pl. LVI. Figs, 2 a, b, c. 

 Reference Plate iii, fig. 12 of this Report. 



Small, teretely conical, somewhat gradually tapering ; surface marked by sharp elevated 

 longitudinal ridges, alternating with finer intermediate ones ; no transverse striae ; septa? 

 siphuncle? section circular. 



This is evidently identical with the species fig. 12 of Plate III. In that specimen, there 

 are no indications of the intermediate finer lines, which are indistinctly visible in the larger 

 specimen fig. 2 a, while they are very distinct in the smaller one. I have been unable to 

 find a specimen showing either septa or siphuncle. 



Fig. 2 a. A fragment imbedded in compact limestone. 



Fig. 2 A. A small fragment, showing the intermediate finer strife. 



Fig. 2 c. A portion of the surface enlarged. 



Position and locality. This species is comparatively rare in New-York, but still has a 

 wide geographical and somewhat extensive geological range ; the one figured on Plate III 

 being found in the upper part of the Calciferous sandstone, while the specimen 2 a is found 

 in the lower part of the Trenton limestone at Watertown. The smaller specimen is from 

 the middle portion of the same rock at Middleville. 



272. 25. ORTHOCERAS LAQUEATUM"? t;ar. a. 



Pl. LVI. Fig. 3. 



This specimen is marked by sharp longitudinal ridges, about equally distant with the 

 stronger ones in the preceding figiues, but having no intermediate ones. The surface is 

 well preserved, and presents an aspect somewhat different from the preceding, and may 

 pcrliaps prove a distinct species. 



Position and locality. In the lower shaly strain of the Trenlon limestone at Middleville. 



