460 



MESOZOIC TIME — REPTILIAN AGE. 



ornata, Lower Oolite, are characteristic forms. The Gasteropods with an entire 

 aperture are still far the most abundant species; but a few genera with a beak 

 exist, and the Purpuroidea (near the modern Purpura) is one example. Except 

 in the great predominance of species with the aperture entire, the Gasteropoda 

 have generally a modern aspect : among them there are the genera Bulla, Ptero- 

 eera, Cerithhim, Fusus, Ncrita, Patella ?, and others. 



(c.) Cephalopods.— Tetrabranchs. — Fig. 730, Ammonites Hnmphreysianw, Lower 

 Oolite ; A. striatulus, Lower Oolite; A. cordatus, Middle Oolite; fig. 731, A. Jason 

 Middle Oolite; A. refractus, Middle Oolite; also species of Ancyloceras and 

 Toxoccras (see figs. 787, 7S9). 



Dibranehs.—Belemnites hastatm, Oxford Clay. Fig. 732, Acanthoteuthis anti- 

 quus, Oxford Clay. Also species of the Calamary and Sepia families, as Cocco- 



Figs. 730-732. 



31 



Cephalopods.— Fig. 730, Ammonites Humphreysianus ; 731, A. Jason ; 732, Acanthoteuthis 

 antiquus (X^a). 



teuthis of the latter. The osselet in the Sepia group is calcareous instead of 

 membranous (p. 156). 



