TRANSACTIONS OF WAGNER 

 584 



TERTIARY FAUNA OF FLORIDA 



drophore, it is elongated and narrow, indicating a first step towards the con- 

 dition found in the next genus. The teeth are elongated on one side of the 

 A and shortened on the other, making the two limbs very disproportionate. 

 There is no modification of the edge of the hinge-plate simulating a lateral 

 lamina, as in Plairodon. 



Genus GLOMUS Jeffreys, 1S76. 

 Shell rounded, the resilium larger and much extended below the teeth 

 posteriorly, the extended chondrophores nymph-like, the limbs of the A- 

 shaped teeth still more unequal, otherwise like Sarcpta, the ligament per- 

 ceptible. Type G. ;«A';/i- Jeffreys, Proc. Roy. Soc, June, 1876. 



Genus MICROYOLDIA Verrill, 1897. 



Shell veneriform, closed, with a distinct external ligament and a strong 

 internal resilium situated on the hinge-plate and not overrun by the posterior 

 line of teeth; teeth few and short, less unequal-sided than in Glomus or 

 Sarepta. Type M. regularis Verrill. 



In the structure of the shell, according to Professor Verrill's figures, this 

 genus differs from Glomus only in minor details. 



The inequality in the sides of the angulated teeth seen in the above- 

 mentioned forms, and also in some species of Leda (ex. L. extenuata Dall), 

 is carried to its greatest extreme in a small Leda-like shell named Silicida 

 fragilis by Jeffreys (1879), where the teeth are reduced to long, imbricated 

 laminae, in which the usual hook at the proximal end is missing. In its other 

 characters SUicula hardly differs from some Yoldias. 



I have included these forms to complete the synopsis of the more modern 

 groups, and also because some of them are represented on our Atlantic coast 

 and may be expected eventually to turn up in our Tertiary beds. 



Leda protexta Gabb. 



While considering matters of nomenclature it seems desirable to clear up 

 a confusion of long standing involving the specific name of protexta in this 

 genus. Several persons have attempted to do this, and each seems to have 

 left a little added confusion of his own, while throwing some light on the 

 subject. 



In March, i860, in the Journal of the Academy of Natural Sciences, 2d 

 Ser., iv., p. 303, Gabb described a Leda pj'otexta from the New Jersey Cretaceous 



