274 



MOLLUSCA. CEPHALOPODA 



usually simple. Suture-liue deeply and finely divided, consisting of 



an external lobe, two lateral lobes, 



and a narrow internal lobe ; of 



an external saddle and two 



lateral saddles. Lateral lobes 



and saddles nearly symmetrically 



divided. Lias to Cretaceous. Ex. 



L. fimbriatum, Middle Lias. 



Hamites. Shell bent upon 

 itself three times, the parts not 

 in contact ; body-chamber long. 

 Suture-line similar to Lytoceras, 

 with the lateral lobes deeply 

 divided. Surface smooth, or 

 ornamented with ribs, tubercles, 

 or spines. Lower Greensand to Chalk. Ex. H. maximus, Gault. 



Macroscaphites (fig. 115). Similar to Lytoceras. Discoidal ; 

 the last whorl produced and then bent back in the form of a hook. 

 Lower Cretaceous. Ex. M. ivani, M. gigas. 



Fig. 114. Lytoceras fimbriatum, 

 from the Middle Lias, x |. 



Fig. 115. Macroscaphites ivani, from the Lower Cretaceous, x £. 



Turrilites. Shell helicoid-spiral, turreted, usually sinistral, 

 all the whorls in contact. Sutures similar to Lytoceras. Surface 

 ornamented with transverse ribs or tubercles. Gault to Chalk. 

 Ex. T. costatus, Chalk. 



Baculites. Shell straight (except a small spiral part at the 

 apex, which is the first-formed part of the shell), elongate-conical, 

 elliptical in section ; body-chamber large, aperture produced at the 



