Die Silnrische Fauna ilex Westlichen Tennessee. 2-47 



shortened, and its sides compressed, as though it had grown between 

 two rocks, and was thereby unable to attain its full size. Posteriorly 

 the shell retains its length, so that the upper and basal margins seem 

 to remain exactly parallel for a distance of fully one half the width of 

 the shell. The beaks contain about six small undulations, yery short, 

 and apiDear nearly parallel, extending lengthwise. 



In the Uhio Sayii we have a full rounded umbo, the basal margin in 

 conformity with this is yery much curyed, regularly approaching the 

 ligament slope, so that the shell posteriorly tapers steadily, and almost 

 uniformly to the posterior margin. The beaks present ten or more 

 undulations or wrinkles ; but we see they more nearly conform to the 

 direction of growth, each succeeding wrinkle being larger and ex- 

 tending nearly around the former, causing the beaks to be wrinkled in 

 the direction of the width, and occupying the first year's growth of the 

 shell-. 



When we examine the internal surface of the yalyes, we readily 

 distinguish those differences in the number and position of the teeth, 

 which are always regarded as of so much importance in classifying the 

 Niades. In the camptodon we have a single cardinal tooth in each 

 valve ; in the Sayii, we have tioo cardinal teeth in the left, and only 

 one in the right valve, a difference sufficient alone to characterize 

 them as distinct species. I trust that I have called attention to 

 enough important points of difference to remove all hesitation about 

 placing the Unifi Sayii in our list of Cincinnati shells, and in excludinsi- 

 the camptodon therefrom. It is really a southern shell, never haviny- 

 been found in this region. 



Mr. Lea. gives as a further list of synonyms for the Uaio camptodon : 

 Utiio declivia, Conrad; JJnio electrinus, Reeve; ITiiio rhomhoideics, Dr. 

 Ward's MSS. ; and Uaio subcroceus, Conrad. 



From Die Silurkche Fauna des Westlichen Tennessee. By Dr. Fer- 

 dinand RcEMER. [Translated by Chas. W. Dietrich, for this 

 journal.] 



Genus Palaomanon. — (Rcemer). 



This is a free sponge, entirely detached, of a cup or goblst form,, 

 displaying upon its upper surfiice large dispersed openings, the space 

 between the openings having the appearance of a very finely punctured 

 web. 



This genus is distinguished from all sponges in the later formations 

 l)y the absence of any epitheca. It is hardly possible to include it 



