TROCHOCERATIDJE. 
19 
an almost exact correspondence with all its characters, but those 
that are flattened and distorted do not agree so well. . . . The 
whorls scareely touch, owing to the want of symmetry. The section 
is elliptic, the long diameter in the plane of curvature being 13| 
lines, when the short is 11 lines. The surface was probably smooth. 
The septa are 32 or even more in half a whorl ; they are nearly 
straight at first and then bend rapidly forward to the front, and 
are almost flat transversely. The siphnncle is external and bulbous. 
The only other smooth, little elevated Trochoceras in British strata 
is T. i07'tuosum, whose section at once distinguishes it. Among the 
Bohemian forms T. unguis has a less proportionate thickness of 
whorl, and T. prisciun . . . has a compressed front [it is also a 
much larger species with wider septa].’’ {Blair,) 
Hoi'izon. AVenlock Limestone. 
Locality. Dudley, Worcestershire. 
Represented in the Collection by a single example. 
Trochoceras priscum, Barrande. 
1848. Trochoceras priscum, Barrande, in ITaidinger’s Berichte iiber die 
^littheil. von Freund, der Natiirwis.'S. in Wien, Baud iv. p. 208. 
1^0)7. Trochoceras prisnnn, Barrande, Svst. Sil. de la Bolieme, vol. ii. 
pt. i. p. 92, pi. xii. ff. 8-11, pi. XV. ff. ll)-19, pi. xix. ff. 12-17. 
Char. Shell consisting of 3 whorls, forming a helicoid spiral. 
Transverse section oval, of which the (slightly) smaller end cor- 
responds with the convex border of the shell. The ratio of the 
ventro-dorsal to the transverse diameter varies between 9 : 8 and 
6 : 5. The rate of increase is but slight, being as 1*: 2 for the two 
external whorls. The body-chamber touches the preceding whorl 
throughout its whole extent : its length slightly exceeds its basal 
diameter. The form of the aperture coincides with that of the 
transverse section. The distance between the septa increases very 
slowly, the maximum attained not exceeding 4 the diameter of the 
shell. Their transverse convexity is slight, but the ventro-dorsal 
reaches | the shell-diameter. The siphnncle is placed close to the 
convex border ; its elements are cylindrical. The test appears to be 
quite smooth. 
Remarks. The species that comes nearest to this is T. anguis., 
Barr. (pi. xvi.), which, however, has a more rounded section and 
closer septa. 
Horizon. Wenlock Limestone. 
Locality. Dudley, Worcestershire. 
Represented in the Collection by a single example. 
c2 
