ADDENDA. ' 2f'0 



Ps. strigilata were procured about Exnioutli in a living state. 

 Since that time, not a single specimen has been found. Like the © 

 shoals of migratory Hsh, it is probable that particular species of 

 shell-lisii resort occasionally to particular localities, and as ab- 

 ruptly disappear. Our cabinet contains some specimens of the 

 Psammobia ta;niata, procured at Exmouth more than twenty 

 years ago, at which time it is supposed they were not uncommon, 

 but since which time not an individual has been found. 



A RCA reticulata, p. 168. 



By the kindness of Dr. Mac Gee, of Belfast, this very beautiful 

 shell is now before us. The breadth is njore than twice as much 

 as the length. One end is rounded, and the other obliquely- 

 truncate. The epidermis is of a pale chesnut, darker towards the 

 ends, under which it is glossy white. From our Area perforans 

 it differs, in being much flatter, thinner, and semitransparent, 

 with the beaks nearer the rounded end. Besides the fine decus- 

 sations which cover the surface, there are about twelve raised 

 longitudinal lines clothed with fine da''k hair. The inside is 

 striate longitudinally ; and what specifically distinguishes it both 

 from the Area perforans and the Area barbata, the inner margin 

 is finely nofclied. 



Dr. Mac Gee also informs us, that the Mya nitida, described 

 by Mr. Wood, p. 10.3, with an obtuse tooth in each valve, has 

 been found at Bangor, in Ireland. 



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