282 
AUG. F. FOERSTE 
location of the hyponomic sinus in this species it is impossible to 
determine with confidence whether this unpaired angle represents 
the ventral or the dorsal side of the conch, but in either event 
the siphuncle of Mixosiphonoceras at least appears to occupy a 
position directly opposite to that in the species previously dis- 
cussed. Moreover, in Mixosiphonoceras the conch is curved 
lengthwise, the siphuncle being located near the concavely 
curved side; the segments of the siphuncle enlarge only mod- 
erately within the camerae, and the interior of the latter is 
occupied by vertical radiating plate-like deposits. 
In the Devonian genus Jovellania, founded by Bayle on Ortho- 
ceras huchi de Verneuil, from Nehon (Manche), France, the conch 
is annulated and its cross-section is only slightly triangular, 
due to a slight flattening of the ventro-lateral sides of the conch, 
causing the median part of the ventral side to be slightly angu- 
lated. There is no corresponding flattening of the opposite or 
dorsal side of the conch. The siphuncle is located near the angu- 
lated median part of the ventral side. Where the dorso-ventral 
diameter is 25 mm. the center of the siphuncle is 6 mm. from the 
ventral angle. The segments of the siphuncle enlarge only 
moderately within the camerae and the interior of the latter is 
occupied by vertical radiating plate-like deposits. 
Compared with typical Jovellania, Orthoceras murrayi is not 
annulated; the siphuncle is located near the strongly flattened 
ventral side of the conch; the form* of this siphuncle is tubular 
instead of moniliform, and the interior of this siphuncle is not 
filled with. radiating vertical plate-like deposits. 
15. Leurorthoceras chidleyense Sp. nov. 
Plate XXXIV, figs, 1 A, B, C, D 
Lateral apical angle 11 degrees. Ventral side gently convex 
or distinctly flattened along its median part; dorsal side much 
more strongly convex. At the lower end of the specimen, where 
its lateral diameter is 39 mm., the radius of transverse curvature 
of the ventral side is 20 mm., that of the dorsal side being 28 
mm. At the top of the specimen, where its lateral diameter is 
