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TERTIARY FAUNA OF FLORIDA 



These differences seem to me sufficient to separate the groups, though 

 perhaps of less than generic value. 



A ininutus ranges from the Claibornian (Alabama, Louisiana, Arkansas) 

 into the Jacksonian, and, after an examination of a great many, only one valve, 

 about twice the usual size, showed the groove for an external ligament. 



Alveinus rotundus n. sp. 

 PLATE 45, FIGURES 25, 28. 



Oligocene marl of the Chipola River, Calhoun County, Florida; Burns. 



Shell resembling A. tninntus Conrad, but smaller, more inflated, more ele- 

 vated, more nearly equilateral, and with a proportionately heavier and more 

 solid shell. No trace of attachment for an external ligament could be found 

 on any of the specimens. Alt. 1.9, Ion. 2, diam. 1.2 mm. 



At first this species was regarded as merely a local race of A. minutus, but 

 the comparison of many specimens showed the characters to be constant, and 

 the difference of horizon in the geologic column is quite marked, so. I have 

 thought it best to treat it as a species. 



The study of these minute forms is very difficult ; even with a compound 

 microscope various lights and a good series are needed to bring out the char- 

 acters. A very slight amount of wear or solution suffices to materially alter 

 the minute teeth, and the observer has to be constantly on his guard against 

 being misled. 



Genus TcreT.T.rRT.T.A Sars. 



This little genus is represented in the Jacksonian by K. Boettgeri O. Meyer, 

 described in the Bulletin of the Alabama State Geological Survey, No. i, p. 

 83, pi. 3, figs. 15, 150, 1886. A recent species, R. nitida Verrill, is known from 

 the Atlantic coast in deep water, and we may expect that other Tertiary horizons 

 when thoroughly searched will prove to include this genus. 



Genus PATJLIELLA Munier Chalmas. 

 Pauliclla (Bernard!) Mun. Chalm., Comptes Rendus, som., 1895, pp. liv.-lv. ; Bernard, 



Bull. Mus. d'hist. Not., 1898, p. 84, figs. 6-7. 



This remarkable little genus resembles Lntctia in a general way, but is 

 characterized by having three anterior laminae in each valve. 



It was among the minute species collected by Velain in the islands of St. 

 Paul and Amsterdam in the Indian Ocean, but was not detected until lately, and 

 is described as above. 



