peroblonga occurs much higher in the Pennsylvania!! system, and the 

 Boggs specimen is too imperfect to render identification with it at 

 all conclusive. The dimensions of the Boggs specimen are: length 

 43 mm., height 20 mm., convexity of right valve 5 mm. 



Horizon and locality. Boggs limestone: near Hopewell P. 0. 

 (Locality 26), r. 



Genus Nucula Lamarck 



Nucula elongata n.sp. 

 PL IV, Figs. 10, 11, 12 



Description. Shell small, sub triangular, much produced anter- 

 iorly, length almost twice the height, greatest width slightly below 

 the middle of the shell, gibbous in posterior portion, the greatest 

 convexity occurring midway between the beaks and the ventral 

 margin, shell flattened anteriorly. Umbonal region prominent, beak 

 small, elevated and incurved over the hinge line, directed posteriorly, 

 situated about one-fourth the length of the shell from the posterior 

 margin; cardinal margin sloping from the beak to the extended anterior 

 extremity; posterior extremity regularly rounded forming a con- 

 tinuous curve with the rounded ventral margin which anteriorly 

 extends slightly upward; anterior extremity produced and pointed. 

 Surface of internal cast smooth except for a few faint lines of growth; 

 occasional indications of fine concentric lines. 



Dimensions. Considerable variation exists in the size of the 

 individuals as may be seen by the following measurements, the first 

 of which is the holotype: 



Maximum length 11 mm. 9 mm. 7 mm. 6 mm. 



Height from beak to opposite 



margin 6.2 mm. 5.5 mm. 4:5 mm. 3.5 mm. 



Thickness of single valve 2 mm. 1.5 mm. 1.2mm. 1 mm. 



Remarks. This species is common in the Sharon ore at a single 

 locality in Scioto County where it occurs in an excellent state of 

 preservation in the form of internal casts. It is related to N. parva 

 McChesney and N. beyrichi von Schauroth, but can be easily dis- 

 tinguished from both species by its much more produced anterior end. 

 It is associated with two other species of Nucula common in the Sharon 

 ore N .subrotundata Girty mss. and N. lunulata Girty mss. 



Horizon and locality. Sharon ore: Lick Run, Scioto county 

 (Locality 2), c. 



Nucula subrotundata Girty mss. 

 PI. IV, Figs. 13, 14, 15 



Description. A species of Nucula from the Sharon ore of Ohio 

 is identical with one described and figured in manuscript by Girty 

 from the Morrow formation of Arkansas. Girty's manuscript descrip- 

 tion is quoted below. 



63 



