&4 THE NAUTILUS. 
supply of this reservoir is pumped from the Schuylkill, where this 
species is abundant; and it was doubtless introduced in the state of 
free-swimming embryos, which found in the muddy bottom of the 
reservoir, a suitable station.—H. A. P. 
PyRAMIDULA ALTERNATA AND GASTRODONTA LIGERA, RE- 
VERSED.—In the collection of the late Ropert WALTON, of Rox- 
borough, Philadelphia, which was presented by his father to the 
Academy of Natural Sciences, a reversed specimen of each of these 
species occurs, both taken in the vicinity of Philadelphia. In a 
former issue we have announced a reversed Z. cellarius found by 
the same ardent conchologist. 
Another sinistral specimen of P. alternata has been presented to 
the Academy, a finely developed shell of the size of ordinary 
adults in this locality. It was found by Mr. Jonn Forp in the 
West Park (Fairmount) some years ago, in a locality now destroyed 
so far as snails are concerned. 
It would seem that sinistral individuals occur more frequently in 
Pyramidula (Patula) than in our other groups of American 
Helices. Binney records a reversed alternata (Man. Amer. L. Sh. 
p. 257) in the Museum of Comparative Zoology. I have seen a 
fine reversed specimen of P. strigosa, in the collection of the late 
Dr. Fr. Srern, of Indianapolis, Ind. I believe that no sinistral 
specimens of American species of this genus other than those men- 
tioned above, have been put on record, but it is not unlikely that 
others exist in collections, unrecorded. If so, we would be pleased 
to hear from their possessors, and to record the occurrence of such 
sinistral Helices as may come to our knowledge.—Ebs. 
Tue Eprror has had the pleasure of very pleasant calls from 
Dr. THEODORE GiuL and Pror. A. E. VERRILL, whose attendance 
at the meeting of the National Academy of Sciences, of which they 
are distinguished members, brings them to this City of Brotherly 
Love. 
ConcHoLocists who do not already possess a copy of Tryon’s 
“ SpRUCTURAL AND SysrEMATIC ConcHOLOGY” should procure it 
now. This work is indispensable to the collector who wishes 
to gain an intelligent idea of the affinities or structure of shells, or 
to classify a collection. The plates illustrate thousands of species 
representing all of the genera and subgenera, and the text contains 
interesting chapters on geographical and geological distribution, 
structure, classification, etc. It is the most complete text book on 
the subject in the English language. 
