70 THE MOLLUSCA OF DORSETSHIRE. 
268. M. costulata (Jsso.) Crenella costulata (Zsso.) 
First notice of it as a British shell in Vol. xix., p. 113, 
* Annals of Natural History,” by Gwyn Jeffreys. 
Weymouth, Damon. 
Fossil: Coralline and Red Crags. 
269. M. discors (Z.) Crenella discors, L. 
Weymouth, rather plentiful; dredged, attached to oysters, 
algee, and zoophytes, W. Thompson. 
Weymouth, in seaweed, Z. R. Sykes. 
Kimmeridge Bay, dredged at various depths, J. C. M.-P. 
Fossil: Chillesford Crag; doubtfully recorded from the 
Coralline. 
co th ioe a sa 
CRENELLA, Brown, 1827. 
The animal does not spin a thick byssus like Modiolaria, but 
secretes a single thread only for attachment by which it 
holds itself suspended in the water. 
270. C. rhombea (Berkeley). Modiola rhombea, Berke/ey. 
Forbes and Hanley, Vol. ii., p. 209, pl. 25, f. 3. 
A single individual of this small and extremely rare shell, the 
average length of which does not exceed the fifth of an 
inch, was dredged at Weymouth, adhering by its byssus 
to a large mass of slate by the Rev. Miles Berkeley, 
Forbes and Hanley. 
Poole, sand-banks (living), Dr. Turner. 
Kimmeridge Bay, dredged, J. C. M.-P. 
Fossil: Coralline Crag. 
AVICULIDA. 
PINNA, L., 1758. 
271. P. rudis, Z. P. pectinata, LZ. 
Pulteney, p. 41, pl. 3, f. 2. 
Forbes and Hanley, Vol. ii., p. 255, pl. 43, f. 1, 2, and 
pl. 53, f. 8. 
Swanage and Studland, thrown up on the shore after a rough 
sea, Pulteney. 
