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TERTIARY FAUNA OF FLORIDA ! 495 



This species is related to Astarte lens of Stimpson and A. nana Jeffreys of 

 the recent fauna, but seems sufficiently distinct. The formation from which 

 these and some other extremely interesting fossils were obtained was named 

 by Dr. Spencer the Coatzocoalcos formation, and its fauna is intimately related 

 to that found in two hundred to four hundred fathoms in Florida Strait or 

 off the coast of Cuba. The present species was at first identified with Astarte 

 Smithii Ball, but subsequent study shows it to be a larger species with narrow 

 furrows between wider concentric ribs, the furrows having a V section, while 

 in A. Smithii the furrows are wider than the ribs and have a flat bottom or 

 channelled section. 



With the advent of the glacial period, the sea along the eastern coast ap- 

 pears to have been cooled, so that many of the Pliocene forms retreated or 

 became extinct, and coincidently an incursion of cold water forms from the 

 north altered the character of the fauna. Among these northern species were 

 quite a number of Astartes, and, as the nomenclature of this group has been 

 v.ery much confused, it seems desirable to briefly review these forms, most of 

 which are still found living in boreal or Arctic waters. This task is much 

 facilitated by the excellent " Observations on the Genus Astarte with a List of 

 the Recent Species" published by Mr. E. A. Smith, of the British Museum, in 

 the "Journal of Conchology," volume iii., pp. 196-232, 1881. A few species 

 have since been added and a few names changed, but, with these exceptions, 

 for the nomenclature of the species of this puzzling group we can hardly do 

 better than accept Mr. Smith's laborious determinations as far as they are 

 available. The important point is to correlate the names used by authors for 

 these Pleistocene fossils with the proper names as determined by Mr. Smith, 

 except in a few cases where the possession of a large series of American species 

 or the progress of science since 1881 has enabled us to note progress in the 

 determination of points at that time in doubt. These have been brought up 

 to date in my recent " Synopsis of the Astartidse with a Review of the Ameri- 

 can Species," to which the reader is referred for fuller details. 



Astarte laurentiana Lyell. 



A. laurentiana Lyell, Travels in N. Am., London, 1845; American edition, vol. ii., pp. 

 125-6, figs. I5a-c, 1845; Dawson, Post-Pi. Geol. Canada, p. 75, pi- vii., fig. 2, 1872, 

 The Canadian Ice Age, p. 235, pi. i., fig. 2, 1893; Whiteaves, Cat. Marine Inv. of 

 Eastern Canada, p. 134, 1901. 



Post-Pliocene: Leda clays of Montreal and other localities in the St. 

 iwrence valley and at Beauport and Riviere du Loup. 



