SCIENTIFIC SUMMARY. 
451 
The following, to which a northern distribution is likewise given, 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 navalis, T. mego- 
tara, T. cMorotica, Solenensis, Machcera costata, Pandora trilinenta, Lyonsia 
hyolina, Maclra soUdissima, Kellia planulata, Macoma fusca, Tellina tenera^ 
Astarte castanea, A. quadrans, A. sulcata, Nucula proxima, Yoldia limatula, 
Mytihis edulis, Elysia cMorotica, Crucihulum striatum, Littorina rudis, L. 
tmebrosa, L,p>aUiata, Lunatia heros, L. triseriata, Nassa trwittata, Melampus 
hidentatus, Alexia myosotis. Many others, not named in the above lists, are 
not limited by Cape Cod ; but as they belong properly to the northern divi- 
sion, they are here omitted. The distribution indicated for our land and 
fresh-water shells is even more erroneous. It is sufficiently evident that 
Cape Cod is in no sense a proper boundary between the northern and southern 
fluviatile and terrestrial species ; but, disregarding this, there are no reasons 
whatever for most of the special indications that he gives. 
G G 2 
