122 



Gems STREPTELASMA. Hall. 



[ Etv. : Stveptoft, twisted; dttsma, lamella.] 



(Pal., N. Y., Vol. L, p. 17.) 



Coralhini .simjjle, turbinate and often curved. Se])ta 

 numerous, those of the earlier cycles all reaching the center, 

 where they are twisted into a jjseudo-columella : those of 

 the last cycles short. Dissepiments present. Epitheca well 

 devel(j})e(l. 



Streptelasm.\ rectum. Hall. (Fig. 2.) (111. Dev. 

 Foss., Pl.XIX.) 



Distinguishing Cliavarters. — Rather small size; conical 

 outline: rapidly tapering toward the base; twisting of the 

 J septa near the center of the calyx, 



and foi-mation of a s(did axis or 

 ])seud()-columella ; slight development 

 of dissepiments; height, 3 or 4 cm.; 

 diameter of calyx, 1 ..1 to 2 cm. 



Found in the lower Moscow shales 

 near the head of Section •"> ; also in 

 the Demissa bed at Section 5, and 

 in the Ti-ilobite beds and the shales 

 below them down to the Nautilus bed, at Section 8, 

 on the Lake Shore, and in the bed of Avery's Creek. It is 

 usu ally abu n d ant . 



Streptelasma unglla. Hall. ( Fig. •>.) 

 (111. Dev. Foss., Pl.XIX.) 



Distinguisliing Cliaracters. — Smaller size than 

 S. recta; less degi-ee of ta]>ering; curved or 

 hoi-n-shaped outline; slight twisting of septa 

 at the center. 

 Fig. 3. strei^t- Fouud ill the lower Moscow shales, between 



elasma ungnla 



(after Hall). ScctlOllS 4 aild ~). 



Fig. 2. Streptelasma rectum 

 (after Hall ). (o) cardinal sep- 

 tum ; (/;) alar sejituiii. 



