CONCHACEA. MOLLUSCA. ■ ASTARTE. 79 



inequilateral, the anterior slope shortest and concave, bearing a long, 

 lanceolate, deeply excavated, smooth lunule ; posterior slope a 

 straight line, usually rounded, but sometimes a little truncated at 

 the hinder end, and including a very long, triangularly excavated 

 corselet ; beaks moderately elevated, pointed, and coming in con- 

 tact ; surface undulated with ten to twenty strongly developed 

 concentric furrows and ridges, the depressed portions wider than 

 the raised ones, vanishing at both ends, covered with a thick, 

 greenish-yellow or glossy, brownish-olive epidermis. Hinge 

 margin strong, two teeth in the left valve and one in the right ; 

 interior polished, bluish-white ; muscular impressions distinct. 

 Length 1 inch, height 1| inch, breadth § inch. 



Very small and half-grown shells are not uncommonly found in 

 the fish of Massachusetts Bay. It has been found by dredging in 

 Newport and Portland harbours ; and occasionally a full-grown 

 specimen is thrown up, with sea-weed attached, on our beaches. 

 I have no doubt it would be found in many places by dredging. 

 Along the coast of Maine it is common. At Augusta, Maine, 

 Dr. C. T. Jackson found it plentifully in a partially fossilized 

 state, and in company with other shells, such as are now com- 

 mon on the coast of Maine, imbedded in the earth many feet 

 above high-water mark, showing, conclusively, that that region 

 has, by some cause, been recently elevated above its former level. 



Tliis shell seems to have caused much perplexity to all who have 

 undertaken to describe it. It is quite uncertain how many real species 

 are embraced in the above synonyms. The discrepancy of authors, 

 and the variety in the form and sculpture of the shells, which must 

 come under one or the other of the names, leaves us in doubt. I have 

 thought best to present them as one, and to include them under the 

 name which seems most appropriate of the three. For, in the first 

 place, the Venus Scotica and V. Danmonia of Montagu are clearly 

 the immature and mature of the same shell ; the distinctive mark 

 which he gives, viz. the smooth margin of the first, and the crenulafed 

 one of the latter, being an insufficient one. He says, " The construc- 

 tion of the margin must be considered as inviolable ; no common shell, 

 whose character is to possess a plain margin, is ever found with a 

 crenulated one, or vice versa.'''' Now, it is perfectly certain, that no 

 species of the genus is found with a crenulated margin, until the shell 



