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Peripetoceras Frieslebeni, Geinitz (Leonh. et Bronn, Jahrb., 

 1841, PL xi, Fig. 1). Figs. 1-3, PI. xi. 



Loc, Tunstall Hill, England, Dyas. 



This shell has a metanepionic substage with a subangular abdo- 

 men and siphuncle propiodorsan. The umbilical perforation is 

 small and a dorsal furrow appears in the paranepionic substage. 

 The apex, as shown in Fig. 1, PI. xi, is narrow and compressed; 

 the metanepionic, Figs, 2 and 3, broadens on the dorsum but 

 remains rounded ; the dorsal furrow at its first appearance, just 

 beyond the gyroceran bend in the paranepionic, is deeper, as shown 

 in Fig. 3, than it is subsequently when opposite the largest diam- 

 eter of the umbilical perforation, Fig. 2, and the whorl changes at 

 the same time from digonal to trapezoidal or temnocheilan-like. 

 The siphuncle, however, remains propiodorsan. 



The neanic substage has a nephritic outline and in the ephebic 

 stage the volution becomes subquadrate with a flattened abdomen. 



The living chamber is somewhat over one-fourth of a volution in 

 length, with broad, shallow, hyponomic sinus, broad, low, lateral 

 crests and sinuses on the umbilical zones. 



The siphuncle continues to be propiodorsan in position. 



The sutures have broad, ventral and dorsal lobes and lateral 

 lobes. There are annular lobes in older stages according to 

 Geinitz. I could find none in the early ephebic stage of the single 

 specimen from Tunstall Hill, which showed a perfect septum, but 

 they may be present in later substages. 



Syringoceras* n. g. 



This genus has been framed for Triassic species like the type, 

 Syringoceras granulosostriahts, which have a tubular, nepionic volu- 

 tion with the siphuncle subventran. The early nepionic shell is 

 also ornamented with very closely set transverse ridges, but it has 

 no longitudinal ridges until a comparatively late stage. This nepi- 

 onic ornamentation is like that of the genus Hercoceras at the same 

 age. The impressed zone is present only after contact and is not deep. 



The genus includes the group of Nautilus Barrandei of Mojsiso- 

 vics, the equivalent of Nautilus linearis, Laube, and S. (Naut.~) 

 evolutum, sp. Mojsisovics. 



Syringoceras (Naut.) granulosostriatus and linearis, stated by 



*Zvpr f c, a tube. 



