200 MANUAL OF THE MOLLUSCA. 
ToxocERAS, D’Orbigny. 
Etymology, toxon, a bow, ceras, a horn. 
Example, T. annulare, D’Orbigny (Pl. III., Fig. 12). 
Shell bow-shaped ; like an ammonite uncoiled. 
Distribution, 20 species. Neocomian, Between this and crio- 
ceras and ancyloceras there are numerous intermediate forms. 
ANCYLOCERAS, D’Orbigny. 
Etymology, anculos, incuryed. 
Synonym, Anisoceras, Pictet. 
Example, A. spinigerum (PI. III., Fig. 10). 
Shell at first discoidal, with separate whorls; afterwards pro- 
duced at a tangent and bent back again, like a hook or crosier. 
Distribution, 88 species. Inferior oolite—chalk. South America 
(Chili and Bogota), Europe. 
ScAPHITES, Parkinson. 
Etymology, scaphe, a boat. 
Example, 8. equalis (Pl. II1., Fig. 9). 
Shell at first discoidal, with close whorls; last chamber detached 
and recuryed. 
Distribution, 19 species. Oolite—Chalk. Europe, India. 
HELICOCcERAS, D’Orbigny. 
Etymology, helix (helicos), a spiral, and ceras, a horn. 
Example, H. rotundum, Sby. species (Pl. Ili., Fig. 11— 
diagram). 
Shell spiral, sinistral; whorls separate. 
Distribution, 11 species. Inferior oolite ?—Chalk. Hurope, 
India. 
TURRILITES, Lam. 
Hiymology, turris, a tower, and lithos, a stone. 
Shell spiral, sinistral; aperture often irregular. 
Distribution, 387 species. Gault—Chalk. Europe. 
The turriite was perhaps dibranchiate by the atrophy of the 
respiratory organs of one side. M. D’Orbigny includes in this 
genus particular specimens of certain Lias ammonites which are 
very slightly unsymmetrical; the same species occur with both 
sides alike. He also makesa genus (heferoceras) of two turrilites, 
in which the last chamber is somewhat produced and recurved. 
T. reflexus (Quenstedt, T. 20, Fig. 16) has its apex inflected and 
concealed, 
