246 



MOLLUSCA. 



Pulmonifera are the Pupa vetusta and Zonites priscus of the 

 Carboniferous Rocks. 



In the following* are given the characters of those families 

 of the Gasteropoda which occur in the fossil state, with the 

 leading genera of each family and their range in time. 



SECTION A. BRANCHIFERA. Respiration aquatic, generally 

 by gills. 



ORDER I. PROSOBRANCHIATA. Gills situated in advance of 

 the heart. 



Division a. Siphonostomata. Mouth of the shell notched, or 

 produced into a canal. 



FAM. i. STROMBID^E. Shell with an expanded lip, deeply 

 notched near the canal. Operculum claw-shaped. Foot nar- 

 row, adapted for leaping. All the existing genera of the 

 StrombidcR are represented in the fossil state, but the family 

 does not seem to have come into existence before the Jurassic 

 period, and it attained its maximum in the Tertiary period. 



Fig. 307. Pteroceras octant. Neocomian. 



The genus Strombus has a shell with a short spire, a long 

 aperture, and an expanded outer lip, there being a posterior as 

 well as an anterior notch. The Strombs are represented in 



* Tn the characters of the families of the Gasteropoda, as in those of the 

 Lamellibranchiata, Woodward's 'Manual of the Mollusca' has been mainly 

 followed. 



