of Shells in the Till near Boston. 



365 



columella, perhaps of Chrysodomus decemcostatus. In the 

 third column are the species found in the cliff of Moon island ; 

 in the fourth column, those obtained from the well at Fort 

 Warren ; in the fifth, those of Peddock's island ; and in the 

 sixth, those of the northern cliff in Hull. At the other locali- 

 ties only Venus mercenaria was found in the limited time 

 available for search. 



List of Species in the Till near Boston. 



Species. 



Balanus crenatus, Bruguiere 



Chrysodomus decemcostatus, Say 



Tritia trivittata, Adams 



TJrosalpinx cinerea, Stimpson 



Lunatia heros, Adams 



Lacuna neritoidea, Gould (?) 



Sasicava arctica, Deshayes 



Mya arenaria, Linne 



Ensatella Americana, Yerrill 



Mactra solidissima, Chemnitz 



Venus mercenaria, Linne 



Tapes fluctuosa, Sowerby (?) 



Cardium Islandicum, Linne (?)... 



Cyclocardia borealis, Conrad 



Astarte undata, Gould 



Astarte castanea, Say 



Mytilus edulis, Linne 



Modiola modiolus, Turton 



Pecten Islandicus, Chemnitz 



Ostrea Virginiana, Lister 



Cliona sulphurea, Verrill 



1 



2 

 * 



3 



4 



5 







* 











* 











* 





* 







* 







* 





* 











* 











* 









•if 



* 

 * 

 * 



* 



* 



* 



# 



* 



* 



« 



* 



* 



# 

 * 







* 



* 



* 



* 





* 



All these species, which remain from the marine fauna that 

 existed before the formation of the last ice-sheet upon this area, 

 excepting one whose determination is doubtful, are found 

 living at the present time in the adjoining waters of Massa- 

 chusetts bay. Stimpson wrote of his collection : " With the 

 exception of Venus mercenaria, I have obtained all of them in 

 a living state by dredging within a mile of the locality where 

 they are now found fossil." Nor are any noteworthy differ- 

 ences observable between these fossils and the living shells, 

 excepting that the Venus inercenaria belongs, like most of the 

 fossils of this species in Sankoty Head, Nantucket, to the very 

 massive and strongly sculptured form, probably not to be re- 

 garded as a distinct variety, which still survives in the waters 

 of Nantucket* 



Four species in this list attain their southern limit at Cape 

 Cod; and one, Tapes fluctuosa, is not reported south of Nova 

 Scotia and the Fishing Banks. The remaining sixteen have a 



*This Journal, III, vol. x, 1875, pp. 369, 371. 



