ONONDAGA-SALT GEOtTP. 



349 



719. 25. PLEUROTOMARL\ PERLATA {n. sp.). 



PL. LXXXIV. Fig. 5 a, b, e. 



Shell depressed ; volutions about seven, flattened above, outer one angular on the margin ; 

 base discoid, depressed towards the large umbilicus ; surface unknown. 



This species, in the character of its volutions, resembles P. lenticularis J but they are more 

 numerous, and more depressed. Numerous imperfect specimens have been obtained, but in 

 none of these is the shell preserved, and they usually consist of fragments of two or three 

 volutions. This species, as well as the preceding, can be readily identified with the figures 

 given. 



Fig. 5 a. View of the upper surface of an imperfect cast. 

 Fig. 5 h. Profile view of the same- 

 Fig. 5 c. Parts of two volutions near the base of the shell. 



Position and locality. In the limestone at Gait, Canada West. 



720. 11. BUCANIA ANGUSTATA (n. sp.). 



PL. LXXXIV. Fig. 6 a, b. 



Volutions narrow, rounded on their sides, expanding near the aperture. 



The specimen figured is a rough cast in limestone, preserving no remains of surface markings. 

 The volutions are less extended laterally than any other species of equal size kno^vn in our 

 strata. 



Fig. 6 a, h. Dorsal and lateral views of the same specimen. 



Position and locality. In the limestone at Gait, Canada West. 



721. 9. CYRTOCERAS ARCTIC AMERATUM (n. sp.). 



PL. LXXXIV. Fig. 7 a-d. 



Elongated, slender, gradually tapering and gently incurved j septa numerous, slightly con- 

 vex ; section transversely oval ; siphuncle dorsal. 



This species possesses some characters in common with C. multicameratum of the Trenton 

 limestone, but the septa are still more closely arranged, and the section in perfect specimens is 

 clearly oval. 



Fig. 7 a. A fragment of a cast, preserving, in a length of two inches, thirty-five septa. 

 Fig. 7 b. A longitudinal section of another specimen. The waved and irregular condition of the 

 septa appears as if due to accidental causes. 



