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TEREBRATULA tetri aedra. 
TAB. LXXXIII. —Fig. 4. 
Spec: Char. Obtusely deltoid, gibbous, plaited; 
front elevated in tbe middle with four or five 
■ sharp plaits ; four or more sharp plaits on each 
-side; beak rather incurved. 
The genera] form of this shell is a regular tetraedron, the 
edges of which are rounded, the plaits are very neat and 
continue to the beak. The distance between the central and 
lateral plaits is about three-fourths the length of the shell. 
This species is plentiful at Aynhoe and in some other 
places, the shell remaining with a silky lustre and some- 
what fibrous texture, like many of its congeners. It is also 
abundant at Banbury in Oxfordshire. 
TEREBRATULA media. 
TAB. LXXXIII.— 2^. 5. 
Spec. Char. Very obtusely deltoid, gibbous, 
plaited; front rounded, with a rising in the 
middle composed of six sharp plaits approach- 
ing those in the middle; beak a little incurved. 
May be distinguished from the last species by its more 
rounded form, the greater number of its plaits, and the less 
sudden elevation of the middle. 
Also from Aynhoe, and the neighbourhood of Bath, 
