70 THE NAUTILUS. 



weathered shells which flourished ten years ago. When mammalian 

 remains can be found with the shells, of course they afford valuable 

 clues. 



The account of Ashmunella begins with an interesting general dis- 

 cussion occupying four pages, in the course of which it is argued, ap- 

 parently on valid grounds, that the ancestor of all the forms had a 

 tridentate aperture. It is to be noted that this is the case with A. 

 thomsoniana pecosensis, the most ancient form yet known. The 

 toothless forms have arisen independently in several localities, and 

 have come to resemble each other so much that they are only sepa- 

 rated readily by those intimately acquainted with the genus, or in 

 some cases by the aid of the anatomy. In this connection I may 

 note that I once found at Pecos, N. M., a toothless shell which was 

 plainly an individual variation of the thomsoniana series ; but anyone 

 could have taken it for A. ashmuni. Recalling this specimen, and 

 more particularly on geographical grounds, I will venture to prophesy 

 that when the anatomy of A. ashmuni becomes known, it will be 

 seen to be related to the thomsoniana series, rather than to the rhy&sa 

 series, where Dr. Pilsbry provisionally places it. 



The classification of the Ashmunellas is as follows : 



(1.) Group of A. rhtssa. A. rhyssa; rhyssa miorhyssa; r. 

 hyporhyssa ; r. townsendi ; altissima ; pseudodonta ; p. capitanensis ; 

 ashmuni; a. robusta (new name = the so-called chiricahuana of the 

 Jemez Mts.). 



(2.) Group of A. thomsoniana. A. thomsoniana; t. porterce ; 

 t. pecosensis — the last a fossil. 



(3.) Group of A. levettei. A. levettei ; I. angigyra (new); 

 /. heterodonta (new; extraordinarily variable); l.proxima(nev?);Jis- 

 sidens (new); duplicidens (new); angulata (new); ferrissi (new, most 

 extraordinary, acutely carinate, with the keel continued up the spire, 

 projecting above the sutures); walkeri ; mearnsi. 



(4.) Group of A. esuritor. A. esuritor (new; aperture tooth- 

 less, anatomy peculiar). 



(5.) Group of A. chiricahuana. A. chiricahuana; c. mogol- 

 lonensis (new). 



(6.) Group of A. metamorphosa. A. metamorphosa (new; 

 shell like chiricahuana, anatomy quite different.) 



The account of Sonorella is not so exhaustive, because the genus 

 has so recently been treated in detail by Mr. Bartsch. The follow- 



