92 THE NAUTILUS. 



different forms. One specimen, a dead shell, which may be of the 

 same, is high, globose, diam. 25, alt. 21 mill., with the last whorl 

 considerably descending towards the aperture, and the latter quite 

 inferior and oblique, somewhat triangular, like that of P. elevata, but 

 there are only a little over six whorls, and the spire is less conical. 



P. thyroides Say. Common at both places, abundant on the hill- 

 top at M; rather large, with strong shell and lip. 



P. pennsylranica Green. A few at P, shell rather high. 



P. mitclielliana Lea. One at P, found by Dr. Ortmann. 



P. palliuta Say. A few at P. 



P. appressa Say. Common at M, mostly young; abundant at P, 

 mostly dead shells. 



P. ivjlecta Say. Common at P, quite small, diam. 9.5-10.5 mill.; 

 color from light to brownish. 



P. tridentata juxtidens Pils. Common at P, small, with a narrow 

 umbilicus, strong lip and high parietal lamina; the curve between the 

 upper and lower " teeth " of the peristome is narrow and rather angu- 

 lar at the periphery, and in most specimens there is an additional thin 

 lamella extending downward and inward from the upper tooth. 

 From ^ts whole configuration this form appears to represent a 

 variety. 



P. fraterna Say. At both places. In some specimens the umbili- 

 cus is covered or nearly so, in others rather open, and the base 

 around the umbilicus is rather excavated, as in P. monodon (Jeai). 

 The surface of all is finely and densely hirsute, and the color is light 

 brown. 



P. stenotrema Fer. Common at P. There are two forms, one of 

 them with a large notch in the peristome, and also otherwise differ- 

 ent, as also seen from other places; a few notes on them will follow. 



Bijidaria contractu Say. One at M. 



B. tappaniana Ad. One at M. 



NOTES ON ORIENTAL TJNIONID^. 



BY L. S. FRIKRSON. 



The following notes are offered as so many "addenda et corri- 

 genda" to Mr. Chas. T. Simpson's great work," The Synopsis of 

 the Naiades : " 



