BRITISH OYSTERS : OLD AND NEW. 205 
VAR. TENBIENSIS. var. novo. 
(Plate xvi., fig. 17). 
This is the oyster described as 0 . edulis by Turton (Brit.. 
Faun., p. 162) as “ suborbicular, rugged, with undulate, imbri¬ 
cate scales, one valve flat and entire, shell varying much in size 
and bulk, generally brown with unequal valves, the upper one 
flat, the lower very convex and rugged, transversely striated 
and often longitudinally ribbed, pearly white inside, beak 
rather oblique, with a row of small knobs running down each 
side/’ and subsequently (Bivalve Shells of the Brit. Isl. 1848) 
as a “ shell roundish oval, with scaly foliations, the upper valve 
less and flattened, and the inner margin very entire.” The 
above description corresponds very well with a large number of 
specimens I have received from Tenby. The Tenby shell 
as a rule does not attain very large dimensions, my largest 
specimen measures 4J inches, breadth 3J inches (100 mm. 
by 90 mm.), but Mr. Ridsdale, F.G.S., tells me that at Water- 
wynd, Tenby, he finds large isolated individuals. One I have 
seen from Caldy Island measures 150 mm. in length by 130 mm. 
in breadth. 
I have separated this as a group, partly because Turton makes 
a specific note of it, and it seems peculiar to West Britain. 
It is very probable that it represents a survival of the original, 
long and massive Celtica group. 
With much hesitation I have referred to the foregoing groups 
as being varieties of the one species 0 . edulis. It is not a matter 
of much importance whether they are so regarded or are not. 
Further research will, I think, show that we are mainly dealing with 
specific and not merely varietal forms. As a rule they have 
nearly all dark coloured plain margins with closely appressed 
laminae on the flat valve, and are characteristic of the Celtic 
province, while those of the South and Atlantic coasts are more 
or less coloured and have the laminations large and extending 
beyond the margins of the upper or flat valve. The loss of these 
usually causes great inequality in the dimensions of the two 
valves, allowing the flat valve to sink into the lower one. 
OSTREA ATLANTIC A sp. novo. 
Lamarck has utilized the name 0 . cristata for a Senegalese 
shell referred to by Adanson (Hist, du Senegal, 1757, pi. 14, 
