OF LABRADOR AND MAINE. 251 



The occurrence of this species is of great interest, as showing that at this point on the 

 coast there was a decided increase in the temperature of the post-pliocene sea, owing prob- 

 ably to the influence of some branch thrown off from the Gulf Stream. Two other shells, 

 members especially characteristic of the Acadian fauna, such as Pandora trilineata, and Leda 

 tenuimlcata, find here their most northern limit. The occurrence of Astarte castanea at South 

 Berwick, mentioned by Dr. C. T. Jackson in his Report on the Geology of New Hamp- 

 shire, is a further proof of the boreal character of these beds, in distinction from the sub- 

 arctic or Syrtensian beds of eastern Maine and the St. Lawrence River. 



The beds at Portsmouth; N. H., as noticed by Dr. C. T. Jackson in his Geological Sur- 

 vey of New Hampshire, are identical with those of Saco and Westbrook. He states 

 therein that Mr. John L. Hayes found Leda (Nucida) portlandica associated with " Bangw.no- 

 laria" at a level thirty feet above high tide, in blue plastic clay. This is the most south- 

 ward limit yet known of Leda portlandica. 



At Point Shirley, as has been shown by Stimpson, the beds dip into the sea 

 over a rocky promontory at an angle of 18°. The forms therein contained are 

 almost exclusively members of the Virginian fauna, being found abundantly in the waters 

 south of Cape Cod, and agreeing precisely with the fossils discovered by Desor in Nan- 

 tucket, and by Red field in Brooklyn, New" York. At this point the Acadian fauna seems 

 to have merged into a more southern assemblage of animals. 



At Point Shirley Dr. Stimpson records 1 the occurrence of the following species, which 

 " occur in the upper part of the stratum of blue clay and pebbles which crops out from 

 under the coarse drift " : — 



Balanus ritgosus, Astarte sidcata, Mytilus modiolus, 



Mya arenaria, Astarte castanea, Ostrcea borealis, 



Solen ensis, Cardita borealis, Fusus decemcostatus, 



Mactra solidissima, Mytilus edulis, Buccinum plicosum, 



Venus mercenaria, Buccinum irivittatnm. 



The specimens which I collected were mostly much worn, as are many of those from 

 New York and Nantucket in the Museum of this Society, collected by Messrs. Desor 

 and Cabot. 



The following species occur in the neighborhood of New York city : — 



Venus mercenaria Lamk. 



Nassa (Llyanassa) obsoleta Say. Specimens of both species are in the Mu- 

 seum of this Society, and agree precisely with those from Point Shirley. 



Our knowledge of the drift beds southward of Point Shirley is comparatively scanty, 

 owing to the few fossils that have been found in these beds, and preserved for future refer- 

 ence. But the interest of the subject is greatly enhanced by the fact, that these strata 

 rest directly upon the middle tertiary beds at Nantucket and Martha's Vineyard, and in 

 the vicinity of New York City, as it would seem from Mather's statements in the Report 

 of the Geological Survey of New York. In addition to this, the fact that the contained 

 fossils are forms now living in the adjacent seas heated by the warm currents thrown off 

 from the Gulf Stream, and thus have almost wholly lost their character as an arctic glacial 

 assemblage, shows that the transition from the cooled areas of the Gulf of St Lawrence 



1 Proceedings Bost. Soc. Nat. Hist. vol. 3, p. 9, 1848. 



MEMOIRS BOST. SOC. NAT. HIST. Vol. I. Pt. 2. 64 



