37« PALAEONTOLOGY OF NEW-YORK. 



LqM'nIltia paraslrtcii (n.s). 



Plate LXXIX A. Fia. 8 a, b. 



Carapace minute, subreniforra, subequivalved, the cardinal line a little 

 concave in the middle ; length about twice the width ; ventral e^ge 

 of the right valve a little oblique : anterior and central tubercles not 

 conspicuous. 



Surface smooth. 



This species is extremely minute, and diflfers in its greater proportional length, 

 and in the concavity of the cardinal margin. 



Fig. 8 a. View of specimen enlarged ten diameters. Fig. 8 6. Profile view of the same. 



Geological position and locality. In the shaly limestone of the Lower Helderberg 

 group; attached to the surface of an Orthoceras. 



Leperditia paniila ( n. s.). 



Plate LXXIX A. Fia. 9 a, b. 



Carapace minute, ovoid, gibbous, the anterior end much narrower than 

 the posterior ; posterior end regularly rounded : ventral margin of the 

 right valve much thickened, and overlapping the left valve ; hinge- 

 line straight. 



Surface minutely punctate (perhaps from weathering). 



This species is scarcely more than half as large as L. parasitica, while its propor- 

 tions of length and breadth are very dilferent. It occurs on the surface of specimens 

 with Beyrichia notata and B. trisulcata, Spirorbis, etc.; and its occurrence was first 

 pointed out to me by Mr. Whitfield. 



Fig. 9 a. A specimen enlarged ten diameters. 



Fig. 9 b. Profile showing the thickened overlapping ventral margin of the right valve. 



Geological position and locality. In the tentaculite limestone : Herkimer county. 



