GEOLOGICAL HISTORY 49 
including the freshwater Cyrenidz, made their 
appearance; while if Corburella be admitted as a 
member of the Septibranchia, that order must be 
added for the first time. The “pens” and ink-sacs 
of earlier members of the Sepza tribe (Beloteuthis and 
Geoteuthis) are first found in the Lias, with the 
remarkable Belemnites whose “ guards,” often called 
“ thunder-bolts,” are familiar fossils. 
In the succeeding Cretaceous period further de- 
velopment took place. Among the Gastropods there 
was a decided increase in the higher Pectinibranchs, 
including representatives of most of the families of 
Rhachiglossa. Amongst Bivalves two most remark- 
able aberrant families (Radiolitidz and Hippuritidz) 
were confined exclusively to this period. Externally 
these look not unlike simple corals with a lid, while 
internally they display highly peculiar modifications. 
Numerous other Eulamellibranchs, including some 
boring forms such as Petricolide and Saxicavide, 
as well as the Razor-fish (Eusis), arose, with an 
undoubted representative of the Septibranchs (Leio- 
pistha). An Octopus (Palgoctopus Newboldi) standing 
for the highest Cephalopods was revealed for the 
first time in the Cretaceous of Mount Lebanon, but, 
on the other hand, the Ammonites and Belemnites 
died out. 
During the Tertiary epoch the Rhachiglossa and 
Toxoglossa became the dominant Gastropods, while 
the Bivalves showed an approximation to present 
4 
