370 
PALAEONTOLOGY OF NEW-YORK. 
Leperditia parasitica (n. s.). 
Plate LXXIX A. Fig. 8 a , b. 
Carapace minute, subreniform, subequivalved, the cardinal line a little 
concave in the middle ; length about twice the width : ventral edge 
of the right valve a little oblique : anterior and central tubercles not 
conspicuous. 
Surface smooth. 
This species is extremely minute, differs in its greater proportional length, 
and in the concavity of the cardinal margin. 
Fig. 8 a. View of specimen enlarged ten diameters. Fig. 8 b. 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 parvula (n. s ). 
Plate LXXIX A. Fig. 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 different. 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. 
