A. E. Verrill on the Mollusca of Europe and N. America. 467 
course, no one will deny that certain species of land-shells 
have been introduced from Europe in modern times by human 
agency ; but, so far as most of the ideutical species are concerned, 
it seems to us far more probable that America gave them to 
Kurope, rather than the contrary, and this whether animals or 
plants, terrestrial or marine. 
north of Cape Cod they are rare or local, viz. :— Cochlodesma 
Leanum, Macetra lateralis, Petricola pholadiformis, P. dactylus, 
Gouldia mactracea, Cytherea convewa, Venus mercenaria, V. no- 
lata, Gemma gemma, Liocardium Morton, Arca transversa, 
Modiola plicatula, Pecten irradians, Ostrea Virginiana, Anomia 
electrica (not of Linn.), Diaphana debilis, Cylichna oryza, Placo- 
branchus catulus, Crepidula fornicata, C. plana, C. convema, 0. 
glauca, lanthina fragilis, Bittium Greenii, Odostomia bisuturalis, 
O. seminuda, Turbonilla interrupta, Pleurotoma bicarinata, P. pli- 
a Nassa obsoleta, Buccinum cinereum, Diacria trispinosa, Lo- 
wo Pealit. eS : 
The following, to which a northern distribution is likewise 
pe, are also found far south of Cape Cod, and many of them 
belong quite as much to the southern as to the northern division ; 
and some of them are decidedly southern, extending even to the 
Gulf of Mexico :—Teredo pst My T. megotara, T. chlorotica, Solen 
ensis, Machera costata, Pandora trilineata, Lyonsia hyalina, Mac- 
; 
