148 HISTORICAL PALAZSON TOLOGY. 
and, with an almost equally cosmopolitan range, survives into 
the Carboniferous period. 
Fig. 97.—A trypa reticularis. Upper Silurian and Devonian of Europe 
and America. (After Billings.) 
The Bivalves (Lamellibranchiata) of the Devonian cali for 
no special comment, the genera Prerinea and Megalodon being, 
Zp MAMI 
a . “ 
TU RWS 
Uf “My (tM \ 
Uf 
“\ 
\\ 
\ 
\Y 
ZZ 
S 
5 
Fig. 98.—Stroshomena rhomboidalis. ower Silurian, Upper Silurian, and 
Devonian of Europe and America. 
perhaps, the most noticeable. The Univalves (Gasteropfods), 
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 /Vatyceras (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 Luomphalus, with 
Vig. 99.—Difierent views of Platyceras du- its discoidal spiral shell. 
ORG aL eee Devonian, Canada. Amongst ae Heteropods, 
the survival of Bellerophon 
is to be recorded ; and in the ‘“ Winged-snails,” or Preropods, we 
find new forms of the old genera Zentaculites and Conilaria 
