70 



THE CHAIN OF LH-^E. 



Tlieir fortunes have thus been precisely the oi)posite of those of 

 the lirachiopods, though in neither case is tlicre very marked 

 elevation or deterioration in the individual animals. A very 

 similar statement may be made as to the sea-snails, whether tlie 



Ik;. Ci2. — Conitlnn'd /i/itii/tosiiitu (^\)n.). A Carboniferous Pteropod, 



curious winged snails (Pteropods) or the ordinary crawlers (Gas- 

 tropods). The former come in early, and are represented by 

 I'alajozoic forms finer than any now extant. Tlie genus Conularia 

 (Fig. 62) presents some Silurian species six inches or more 



Fir;. 63. — Silurian Sea-snails. Canada. 



a, Murchisonia hicincta (Hall), b, ricurolottinria uiiihilhutiiln {}\\\\\). c, Miirchisniiia 

 i'r<(C/V/i' (Hall), d, Ih'ilcro/>/ion suicututm {^i'AW'in^'^). 



in length, which arc giants in comparison with any now 

 living. The forms of more ordinarv (iastropods from the 

 Silurian represented in Fig. 63 will suffice* to show that their 

 styles are not very dissimilar from those still extant. As in 



