76 THE HAMILTON ASSOCIATION. 



if for nothing else. Oliva Porphrynia (the types) is one of the most 

 exquisitely colored shells known, and Mrs. Carey's collection con- 

 tains some very fine examples from Lower California. 



Another type is Oliva iiiflata (Lamark from Singapore). The 

 common name for the former is the " Camp Olive," suggested by 

 the white tent-like markings. It is said by Professor Ward, of 

 Rochester, to resemble a multitude of pale mountain peaks rising 

 from a deep brown mist. 



Oliva incrassata is greatly admired also. Ward, of Rochester, 

 a well-known experienced dealer, states : " It is a remarkable fact 

 that. Oliva heatula^- of Panama, occurs also abundantly on the west 

 coast of Africa." Now if there can be no mistake in the matter, it 

 is of considerable importance from a Geological point of view. 

 Darwin mentions in his journal, referring to Purpura patiila^ which 

 is found both on the eastern and western coasts of America : " The 

 dispersion of this coast shell may perhaps have taken place at the time 

 when the channel of the River St. Cruz formed a strait joining the 

 Atlantic and Pacific Oceans." Such a passage as this would prob- 

 ably influence the direction of the Gulf Stream. The author of 

 " The Manual of the MoUusca " remarks : " If it is true that any 

 number of living species are common to the Pacific and Atlantic 

 shores, it becomes probable that some portion of the Isthmus of 

 Darien has been submerged since the Eocene Tertiary period. Any 

 opening of this barrier would allow the equatorial current to pass 

 through into the Pacific ; there would be no more Gulf Stream ; the 

 climate of Britain from this cause alone might become like that of 

 Newfoundland at the present day." 



TURBO (top shell) — TROCHUS (hOOP SHELL). 



In accordance with the views of Woodward — and Mawe about 

 the first quarter of the century, — Professor Ward considers the 

 above are fairly entitled to family distinction. Woodward, on the 

 other hand, includes both as Turbinidce. It must be admitted there 

 is a slight difference in the apertures, and while Turbo possesses a 

 solid calcarious operculum, Trochus has a horny multi-spiral one, 

 and is also more conical in shape. The living occupants of the 

 respective shells do not differ essentially. The nacreous lustre of 

 the interior seems common to both. There are two members which 



