W. Ujpham — Recent Fossils near Boston. 203 



3. At City Point, the east extremity of South Boston 

 (known as Dorchester Heights in the history of the Revolu- 

 tion), dredging is in progress for deepening an adjacent part of 

 the harbor, and the mud and sand thus removed are used in 

 the extension of City Point for the site of the Marine Park. 

 The depth of water where the dredging is being done, mid- 

 way between the Point and Castle Island, is about ten feet 

 below mean low tide, and the excavation goes several feet 

 lower, bringing up abundant fossil shells. Twenty-one species, 

 noted in the third column, have been identified here. 



The four species mentioned for their abundance in the 

 Charles Elver are also very plentiful at City Point, having 

 similar large size, which shows that in both places they had 

 favorable conditions for luxuriant growth. Chief among these 

 conditions are mild temperature and clearness of the water, 

 such as are found in estuaries and shallow bays, sheltered from 

 the Waves of storms. 



Taken as a whole, the twenty-five species comprised in the 

 identified fauna of the three localities belong in their present 

 geographic range to a somewhat more southern and warmer 

 portion of our coast. Fourteen are distinctly southern, and 

 reach their northward limits at Cape Cod or in Massachusetts 

 Bay, and in one instance near Portland, Maine ; excepting 

 that several of them occur in isolated colonies far north of 

 their general and continuous range, as in Casco and Quahog 

 Bays, Maiue, and especially in the shallow southern part or 

 Acadian Bay of the Gulf of St. Lawrence, from Cape Breton 

 Island to the Bay of Chaleurs.* The occurrence of these 

 southern mollusks, which are mostly now absent, or local and 

 rare, north of Cape Cod, shows that the sea here during some 

 part of the Recent epoch lias been warmer than at the present 

 time. Six of the fourteen, namely, Iyanassa obsoleta, Uro- 

 salpinx cinerea, Mulinia lateralis, Venus mercenaria, Modiola 

 plicatula, and Ostrea Virginiana, occur in each of the three 

 localities noted, and indicate the contemporaneousness of these 

 deposits. All of the eleven northern species, some of which 



* After the presentation of this paper before the Boston Society of Natural 

 History, the author learned of Mr. W. P. Ganong's admirable memoir. " Southern 

 Invertebrates on the Shores of Acadia," published a few months ago in the 

 Transactions of the Royal Society of Canada, vol. viii, sec. iv, for 1890, pp. 167— 

 185. Mr. G-anong gives a history of the discovery of the character of the colo- 

 nies ; a list of marine invertebrates belonging to the Virginian fauna, which occur 

 upon the coasts of Acadia and Maine, with tabular reference to their known 

 localities; and a discussion of their recent extinction on intervening portions of 

 the coast thence south to Massachusetts Bay and Cape Cod. He accepts the ex- 

 planation of Verrill and Dawson, noticed on a following page, for the present 

 refrigeration of the sea here ; but also points to the recent increasing severity of 

 cold in Greenland and Iceland, and suggests that the marine currents there like- 

 wise have been lately warmer than now. 



