dr 
from the Gulf of St. Lawrence. —— 451 
of distinct specific rank ; but, considering the small number 
of specimens at my disposal for examination, I have thought 
it better to err, if err I must, by allowing too much latitude to 
variation, rather than by unnecessary species-splitting. The 
variation, though in most cases such as to be almost incom- 
municable by drawings or written description, is nevertheless 
sufficient to be puzzling, consisting in very slight modifications 
of the shell in almost all directions—in outline, proportions, 
and degree of surface-ornament. Such remarks as I have 
thought it necessary to make on these points will be found 
under the names of the different species. 
It would be unwise to generalize hastily from the small 
number of dredgings here described; yet we cannot help no- 
ticing that the general facies of this fauna much more nearly 
approaches to that of the Shetland seas or of the Scottish glacial 
clays than it does to that of England, while it has scarcely 
any thing in common with that of the Mediterranean. The 
species which give it an emphatically boreal character are 
Cythere leioderma (perhaps the most abundant species in these 
dredgings, and hitherto found only in the Shetland seas), C. 
emarginata, C. costata, and Cytheridea Sorbyana, all of which 
may be said to range, on our side of the Atlantic, north of the 
60th degree of north latitude. And several other members of 
the list become with us very scarce south o : these are 
Cythere concinna, C. lutea, C. tuberculata, C. dunelmensis, 
|. Cytheridea papillosa, and C: punctillata. Except the three 
species here described as new, these two lists include all the 
characteristic species of Dr. Dawson’s dredgings, the rest being 
represented in each case only by one or two specimens, often 
imperfect. 
Argillecia, sp. 
One specimen, possibly referable to A. cylindrica, Sars. 
Cythere leioderma, Norman. (Pl. XIX. figs. 11-13.) 
(Norman, Shetland Dredging Report, p. 291.) 
Carapace, as seen from the side, subquadrate, slightly higher 
in from: than behind; greatest one situated at the anterior 
third, and equal to about half the length ; anterior extremity 
obtuse, obliquely rounded ; posterior subtruncate, sinuated in 
the middle: superior margin scarcely arched, obsoletely an- 
