298 
NAUTILOIDEA. 
very distinct constriction runs around it just below its margin. The 
distance between the sejjta amounts to about ^ the diameter of the 
shell; their convexity equals ^ of the same. The siphuncle is 
situated close to the concave border, without, however, touchiog it : 
it is somewhat nummuloidal. The test is ornamented with trans- 
verse, somewhat prominent, raised lines, the surface of which 
appears to be smooth. • ^ 
Remarlcs. This species is readily distinguished by its small size 
and characteristic curvature. 
Horizon. Etage E (= Salopian). 
Locality. Konieprus, Bohemia. 
Represented in the Collection by two examples. 
c. Medioyastrlc h 
Loxgicoxes. 
Cyrtoceras (Meloceras) extricatoim, Blake, sp. 
1839. Lituites articulafus, J. de C. Soweib}’, in Murchison’s Sil. Syst. 
pt. ii. p. 622, pi, xi. f. 7 {not ff, 5, 6 ). 
1882. Cyrtoceras exti'icatum, Blake, British Foss. Ceph. pt. i. p. 183, 
pi. V. ft. 10, 11, 11«. 
1852. Lituites articulatus, M^Coy, British Pal. Foss. fasc. ii. 
p. 323. — 1873. Lituites articulatus, Salter, Cat. Cambr. Sil. Foss, 
p. 174.] 
S_p. Char. “ The section is circular. The rate of increase in the 
septal portion is unseen, the example chosen as type consisting 
of body-chamber only, which decreases towards the aperture. 
The mean radius of curvature is 2^ inches at a diameter of |- 
inch. The body-chamber is four times as long as its basal diameter. 
The aperture is circular, and not marked by any constriction. 
The ornaments are strong radial non-separate ribs, about 5 the 
diameter apart ; the shell-surface is not preserved. The septa are 
parallel to the ribs, and the convexity is nearly equal to their 
interval. The siphuncle is small and nearly central. 
. . . “ This species has entered into the confusion that has 
arisen over the curved and straight transversely-ribbed species. 
First, Sowerby thought it might be the straight portion of his 
Lituites articulatus — now Ophidioceras. The distinctness of the 
latter has long been seen. Next, the quite straight Orthocerata 
^ =.Aylocerus, d’Orb. (Prodr. vol. i. p. 112), instituted for “ Cyrtoceras in 
which the siphuncle is subcentral instead of being marginal.” 
