OF NORTHUMBERLAND AND DURHAM. 103 
Fusus antiquus and gracilis, Cyprina Islandica, and Modiola 
vulgaris, from their size and frequent occurrence, form a conspi- 
cuous part of our Fauna, but their general diffusion through 
most of the British seas prevents our considering them as charac- 
teristic of this locality. These species, however, are rare on the 
southern coast of England. Of northern forms, whose absence 
is deserving of remark, perhaps the most conspicuous is Lottia 
testudinalis, so widely spread in northern latitudes and abundant 
on many parts of the west of Scotland, as well as in Ireland and 
Wales. This species does not appear to inhabit any part of the 
eastern coast of Britain. Other northern species, not uncommon 
on the western shores of Scotland, are also absent here ; of these 
we may mention Lima hyans, Terebratula caput-serpentis, Cra- 
mia anomala, Pecten niveus, and nebulosus, Leda pygmea and 
Margarita carnea. The following south of England species do 
not occur with us,— 
Bulla hydatis, Ovula patula, 
Eulima polita, Fissurella reticulata, 
Scalaria clathratula, Calyptrea Chinensis, 
Truncatella Montagui, Modiola Gibbsii, 
Tanthina fragilis, Arca lactea, 
Rissoa crenulata, Cardium aculeatum, 
striatula, exiguum, 
Phasianella pullus, Cytherea chione, 
Trochus umbilicatus, Tellina depressa, 
striatus, Petricola irus, 
crassus, Pandora obtusa, 
Pleurotoma gracilis, Galeomma Turtoni, 
septangularis, Gastrochena pholadia, 
purpurea, Pholas parva, 
Fusus muricatus, papyracea, 
Erato levis, dactylus. 
These may all be considered southern forms which have not 
reached our limits, but it is worthy of remark that some of them 
attain a much higher latitude on the western side of Great Bri- 
tain than they do on the eastern. Many others might be added, 
