68 TESTACEA. 



On the whole, this species bears much resemblance to the Modiola 

 in every thing, so that it is doubtful whether we shall judge it other than 

 a variety, subject to the accidental formation of spines, from some pecu- 

 liarity of the epidermis. 



I have seen but one specimen, of small size, with spines. However, 

 this favours the opinion of the M. hnrhata being a distinct specimen. 



Plate XII. 



Figs. 5, 6. Modiola barhata. 



Modiola discrepans — The Corded or Corduroy Mussel. — Plate XII. 



Fig. 7. 



Perhaps, doubts may be entertained, whether, in the most rigid dis- 

 tribution, this subject should be associated with either the Mytilui^ or 

 Modiola, in their restricted application. 



Shell a rude oval, extending eighteen lines by nine ; dark bluish 

 grey without, white within ; thin and light. The surface deeply striated 

 from the umbo of each valve to the circumference, particularly conspicu- 

 ous towards the broader end, where the edges are crenate. It shines as 

 if varnished. The foot of the animal inhabiting it is white. 



This is the only shell of the whole testaceous tribes which the 

 Scotish fishermen seem to account of any value. They offer nothing else : 

 formerly, specimens were sold to collectors for half-a-crown. 



The species is comparatively rare. 



Plate XII. 



Fig. 7. Modiola discrepans — The Corded Mussel. 



3. Anodon avonensis (A. cijgmus). — Plate XIII., Fig. 3. 



Shell rudely oval ; three inches and a half by two. Subject com- 

 pact, hea\7^. 



