CTRTOCEEATID^. 
277 
Cyrtoceras (Meloceras) cycloideum, Barrande, sp. 
1867. Cyrtoceras cycloideum, Barrande, Svst. Sil. de la Bolieme, toI. ii. 
pt. i. p. 589, pi. cxli. ff. 16-25. 
Sp. Char. This species is among the number of those which 
represent the maximum of cnrvatnre in Cyrtoceras ; it forms in fact 
almost a complete whorl. Xo specimens have, however, been col- 
lected with the apex perfect. The transverse section is oval. The 
ventro-dorsal diameter is to the transverse nearly as 5:4. The 
rate of increase is in the ratio of 2 to 3, in a length of 30 miOim. 
of the septate part of the shell. The body-chamher occnpies about 
4 of the total length of the shell, making allowance for the missing 
portion. A row of crenulations encircle it in an oblique direction, 
about halfway between the base and the aperture. The septa are 
distant from each other about ^ of the ventro-dorsal diameter. 
The siphuncle is situated on the convex border of the shell; its 
elements are slightly inflated between the septa. The test presents 
only fine lines of growth upon its surface, these form a well-marked 
sinus upon the peripher}’. 
Remarlcs. M. circumfleamm, Barrande (pi. cxx.), comes very near 
to the present species, but the siphuncle is cylindrical. Other allied 
species are M. patiens, Barr., and M. discoideum^ Barr. 
Horizon. Etage E ( = Salopian). 
Localities. Lochkow, Dlauha Hora, Bohemia. 
Fairly well represented in the Collection. 
Cyrtoceras (Meloceras) cyclostomum, Barrande, sp. 
1867. Cyrtoceras cyclostomum, Ban’ande, Syst. Sil. de la Boheme, vol. ii. 
pt. i. p. 494, pi. cliv. ff*. 1-10, pi. clvii. ff. 9-12. 
Sp. Char. The greater number of examples of this species have 
only a very slight curvature. Upon a chord of 50 millim., subtending 
the concave side, the highest perpendicular is only 2 millim. The 
transverse section of the shell is nearly circular. The rate of in- 
crease is in the ratio of 1 to 2, in a length of 20 millim. of the 
septate part of the shell. The body-chamber is a little inflated in 
the upper part and narrows towards the aperture, where a slight 
constriction can be seen in the cast, so that the shell is somewhat 
fusiform in outline. The distance between the septa amounts to 
about ^ the diameter of the shell. The siphuncle is situated on 
the convex border. The surface of the test is marked only with 
lines of growth. 
EemarJcs. The very slight curvature of the shell and the inflation 
of the body-chamber distinguishes this species from its congeners. 
