LEDA. 157 



Beechey has dredged it alive in 145 fathoms off the 

 Mull of Galloway. It occurs in all our upper tertiary 

 deposits, although in all probability an allied species 

 (L. pernula, Miiller) has been often mistaken for it in 

 compiling lists of fossil shells. The variety has a more 

 southern habitat, and is found on all the English, Welsh, 

 and Irish coasts, as well as at Oban and in the Hebrides. 

 Both the typical form and variety frequent the Arctic 

 and Scandinavian seas, at depths of from 10 to 160 

 fathoms. Gould has recorded this species from Massa- 

 chusetts, and observed that he could find no difference 

 between the American shell and a specimen of L. minuta 

 from Norway, which had been sent to him by Dr. Loven. 



Specimens vary very much in convexity and the de- 

 gree of striation. Those obtained from deep water are 

 usually flatter, and more delicately grooved, while spe- 

 cimens from comparatively shallow water are more or 

 less tumid, and have stronger ribs. The flat and fine- 

 ribbed form has been taken by Dr. Torell at Spitz- 

 bergen. The fry have no ribs, but the cross lines are 

 very conspicuous. 



Loven has not given any reason why he considers the 

 Area minuta of Montagu is not that of Fabricius, and 

 this eminent conchologist has strangely omitted the 

 authority of O. F. Miiller for that name. Three years 

 after the publication of his ' Prodromus ' to the ' Zoo- 

 logia Danica/ Miiller described L. pernula ; so that he 

 was evidently aware of the difference between the two 

 species. Both are found living side by side in the "north- 

 ern seas. L. pernula is the Nucula oblonga of Brown, 

 which is not uncommon in the Clyde beds; and Stimp- 

 son has enumerated it among the pleistocene fossils lately 

 collected by Mr. Drexler in Hudson's Bay. It may be 

 identical with the N. cuspidata of Philippi, from the 



