BLACK-RITER LIMESTONE. 53 



Plate XIII. 



Fig. 1. Lateral view of a specimen. A part of the last volution, near the aperture, is broken off 



Fig. 1 a. Lateral view of the cast of a smaller specimen. 



Fig. 1 h. Dorsal view of the same specimen. 



Fig. 3. A section apparently of the same fossil, though the surface markings arc not preserved. The 



septa are distinctly shown in a portion of the shell, and lh(; dorsal siphon at two points a, a. 



I have not been able to ascertain positively the position of the siphon in the other specimens 



bearing the shell, figs. 1 and 1 a. 



Plate XIII. (bis). 

 Fig. I. A large specimen, showing a part of the fossil denuded of the shell, the direction and distance 

 of the septa, and a portion of the deep outer chamber, the extremity being broken off 



I am indebted to Dr. Crawb for the use of thi.s fine specimen, as well as for that on 

 Plate XIII. fig. \. 



Position and locality. This fossil is known to me only as occurring at Watertown, Jef- 

 ferson county, in the Black-river (or ^'■seven-foot tier" of) limestone, being unknown in 

 any higher position. "" (State Collection.) 



87. 2. LITUITES CONVOLVANS? 



Pl. XIII. Figs. 2, 2 a. 



Compare Lituites convolvans. Hisingeh, Pet. Suecica, 1837, pag. 27, pl. S, fig. 6; Anteckn V. tab. v. fig. 1, 2. 

 Lihdtes imperfectim. Wahlenberg, Nov. Act. Reg. Soc. Sci. Upsal, 1821. 



Convolute, discoidal, gradually enlarging ; volutions about two or three, scarcely con- 

 tiguous, outer one separating and continued in a direct line towards the aperture ; surface 

 smooth?; section circular; septa plain, moderately concave, direction oblique from the 

 inner side of the volution outward and upwards ; siphuncle dorsal? 



Two or three specimens of this species have been discovered, where exposed upon the 

 weathered surface of the limestone, w'hich is too compact to allow of separating perfect 

 specimens. So far as can be determined, the surface is smooth and the section circular. It 

 is evidently closely allied to the L. convolvans ut supra, and probably identical with that 

 fossil, which is found in the older limestone of Sweden. 



Fig. 2. A portion of a cast, showing the septa and part of the outer chamber. 



Fig. 2 a. A vertical section of another individual as seen on the weathered surface of the limestone, 

 showing the septa, which are removed from the smaller extremity by weathering. The cast 

 is worn down below the siphuncle, which has not been observed in any specimen yet seen. 



Position and locality. In the Black-river limestone, associated with large numbers of 

 Orthocerata. Watertown, Jefferson county. 



