102 ARCID^E. 



area, or the cavity behind the beaks, narrow, striated trans- 

 versely : cartilage small, but thick and strong, yellowish, con- 

 tained in a shallow triangular pit or depression, which is 

 placed immediately under the beaks, and lies between them 

 and the hinge-plate : hinge-line nearly straight, interrupted 

 by the cartilage-pit : hinge-plate very broad, occupying scarcely 

 one-fourth of the circumference of the shell: teeth, about a 

 dozen, strong, somewhat curved, and set obliquely : inside 

 porcellanoua and glossy, remotely and indistinctly striated 

 lengthwise, bevelled off towards the margin, so as to form a 

 broad and smooth edge : pallial and muscular scars very dis- 

 tinct. L. 0-385. B. 0-385. 



Hahitat : Off Unst, the most northerly of the Shet- 

 land Isles, in 85 fathoms, sandy gravel. Altogether 

 four living examples, a large and perfect dead one, 

 and several single valves of different sizes have been 

 found. Capt. Hoskyn obtained two small valves in a 

 Bllbfossil state from a sounding at 340 fathoms off the 

 west coast of Ireland. It is not an uncommon shell in 

 the Coralline Crag at Gedgravc ; and Mr. Scarles Wood 

 says his cabinet contains one specimen from the Red 

 Crag, but it is much waterworn. I have also found it 

 in upper mioccne strata in the south of France ; and it 

 has been recorded from the same formation in other 

 parts of the Continent, as well as from the Subapen- 

 ninc tertiaries, where Brocchi first discovered the spe- 

 cies. Michclotti must have been mistaken in citing 

 it as still living in the Mediterranean. 



The animal is very shy, and perhaps feels uncomfort- 

 able at being disturbed and removed from its native bed. 

 No part of it was visible in the first specimen which I 

 captured (in 18G2), although I watched it for a long time. 

 The shell is a lovely object when fresh and examined in 

 water. The long and delicate but stiff hairs of its epi- 

 dermis resembled a fringe of silken eyelashes surround- 

 ing the lids of a sleeping beauty ; and it was exceedingly 



