38 AUG. 'k FOERSTE 



at the base of the limestone near the old abandoned cement mill 

 at the southwestern end of the town, and of a specimen of Stropho- 

 mena planodorsata . 



The form of Rhynchotrema capax found at the base of this 

 limestone is much more abundant at the top of the limestone 

 and in the overlying Richmond clay ; it is most numerous near 

 the top of the clay, one specimen being found even included in 

 the Clinton rock, half an inch above its base. This form differs 

 from the Rhynchotrema capax of the Richmond of Ohio, Indi- 

 ana, and Kentucky, chiefly in size. It is smaller ; the largest 

 and most obese specimen so far found does not exceed 20™*" 

 in thickness and 16™™ in width. It is also more narrow, and 

 while the typical specimens from the Richmond of Indiana and 

 Ohio have five distinct plications on either side of the fold of 

 the dorsal valve, the Tennessee specimens here described have 

 seven, and occasionally even eight, plications. The internal 

 markings are the same. It may be called Rhy?ichotreina capax 

 manniensis. 



The dorsal valve oi Strophome?ia planodorsata'^ is slightly concave 

 over an area exceeding half the length of the shell, and has a 

 flat appearance over an area equaling two-thirds of its length. 

 The striae are even finer than those figured by Winchell and 

 Schuchert. One specimen occurred nine and one-half feet above 

 the base of the Richmond limestone and others were found near 

 the top. Rafinesqui7ia alteniata, Plectambonites sericeus, and Heb- 

 ertella sinuata also occur. 



The most interesting fossil is a species oi Lingidops belonging 

 to the subgenus typified by Li?igulops granti,'^ a Silurian species 

 from Hamilton, Ontario. It agrees in having the muscular area 

 of the pedicle valve developed into a well-defined platform the 

 anterior edge of which is not prolonged into a septum. Its 

 length is 6""". The median impression between the central 

 muscular scars is relatively more narrow ; the platform does not 

 extend as far toward the beak ; the position of the pedicle may 

 be recognized. The name Lmgidops cliftonetisis is suggested. 



' Minnesota Geol. Surv., Vol. Ill, Part I, p. 393. 

 ''Pal. New York, Vol. VIII, Part I, PI, IV K, Fig. 15. 



