14^ 



HISTORICAL PAL/EONTOLOGY. 



and, with an almost equally cosmopolitan range, survives into 

 the Carboniferous period. 



Fig, 97. — Atrypa reticidaris. Upper Silurian and Devonian of Europe 

 and America. (After Billings.) 



The Bivalves {Lamellibranchiafa) of the Devonian call for 

 no special comment, the genera Fkrhiea and Alegalodoii being, 



Fig. 98. — StropJwinena rJwniboidalis. Lower Silurian, Upper Silurian, and 

 Devonian of Europe and America. 



perhaps, the most noticeable. The Univalves {Gasteropods), 

 also, need not be discussed in detail, though many interesting 

 forms of this group are known. The type most abundantly 

 represented, especially in America, is Platyceras (fig. 99), 



comprising thin, wide - 

 mouthed shells, probably 

 most nearly allied to the 

 existing •'Bonnet-limpets,'' 

 and sometimes attaining 

 very considerable dimen- 

 sions. We may also note 

 the continuance of the 

 genus Eiiomphahis, with 

 its discoidal spiral shell. 

 Amongst the Heteropods, 

 the sur^'ival of Bellej'opho7i 

 is to be recorded ; and in the '' Winged-snails," or Pteropods^ we 

 find new forms of the old orenera Tentacidites and CoJiularia 



Fig. 99. — Different views of Platyceras dii- 

 inostim, of the natural size. Devonian, Canada. 

 (Original.) 



