1 i THE MODERN PERIOD. 



to the southward an extensive semicircular bay, 200 miles in 

 diameter, which we may call the great Acadian Bay, and on the 

 north the larger and deeper triangular area of the Gulf of St Law- 

 rence. This Acadian Bay is a sort of gigantic warm-water aquarium, 

 sheltered, except in a few isolated banks which have been pointed 

 out by Mr Whiteaves, from the cold waters of the gulf, and which 

 the bather feels quite warm in comparison with the frigid and often 

 not very limpid liquid with which we are fain to be content in the 

 Lower St Lawrence. It also affords to the more delicate marine 

 animals a more congenial habitat than they can find in the Bay of 

 Fundy, or even on the coast of Maine, unless in a few sheltered 

 spots, some of which have been explored by Professor Verrill. It 

 is true that in winter the whole Acadian Bay is encumbered with 

 floating ice, partly produced on its own shores and partly drifted from 

 the north ; but in summer the action of the sun upon its surface, the 

 warm air flowing over it from the neighbouring land, and the ocean 

 water brought in by the Strait of Canseau, rapidly raise its tem- 

 perature, and it retains this elevated temperature till late in autumn. 

 Hence the character of its fauna, which is indicated by the fact, that 

 many species of molluscs whose headquarters are south of Cape Cod 

 flourish and abound in its waters. Among these are the common 

 oyster, which is especially abundant on the coasts of Prince Edward 

 Island and Northern New Brunswick, the Quahog or Wampum shell, 

 the Pdrlcola pholadiformis, which, along with Zirfea crispata, 

 burrows everywhere in the soft sandstones and shales ; the beautiful 

 Modiola plicatula forming dense mussel-banks in the sheltered coves 

 and estuaries ; Cytherea (Callista) convexa ; Cochlodesma leana and 

 Cummingia tellinoides ; Crepidula fornicata, the slipper-limpet, and 

 its variety unguiformis, swarming especially in the oyster-beds ; 

 Nassa obsoleta and Buccinum cinereum, with many others of similar 

 southern distribution. Nor is the fauna so very meagre as might 

 be supposed. My own collections from Northumberland Strait in- 

 clude about fifty species of molluscs, and some not possessed by me 

 have been found by Mr Whiteaves. Some of these, it is true, are 

 northern forms, but the majority are of New England species. 



The causes of this exceptional condition of things in the Acadian 

 Bay carry us far back in geological time. The area now consti- 

 tuting the Gulf of St Lawrence seems to have been exempt from the 

 great movements of plication and elevation which produced the hilly 

 and metamorphic ridges of the east coast of America. These all die 

 out and disappear as they approach its southern shore. The tran- 

 quil and gradual passage from the Lower to the Upper Silurian 



