84 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 ROBERT 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. JOHN FORD in the 

 West Park (Fairmouut) some years ago, in a locality now destroyed 

 so far as snails are concerned. 



It would seem that sinistral individuals occur more frequently in 

 Pyramiduta (Patula) than iu 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. STEIN, 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 

 siuistral Helices as may come to our knowledge. EDS. 



THE EDITOR has had the pleasure of very pleasant calls from 

 Dr. THEODORE GILL and PROF. 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. 



CONCHOLOUISTS who do not already possess a copy of Tryon's 

 " STRUCTURAL AND SYSTEMATIC CONCUOLOGY " 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. 



