1905.] NATURAL SCIENCES OF PHILADELPHIA. 225 
The jaw and teeth of Ashmunella do not differ from those organs in 
Sonorella. The jaw is ribbed, the ribs variable and irregular, as is often 
the case in the Californian Helices. It is less strong and the ribs are 
less convex than usual in the jaw of Polygyra. The radula has from 
24.1.24 to about 30.1.30 teeth. There are 9 to 12 lateral teeth. In 
nine of the ten species examined, both mesocone and ectocone are bifid 
on part of the marginal teeth. In A. duplicidens and A. chiricahuana 
the ectocone is usually simple, but on occasional outer marginals of 
the latter they are bifid, as in the other species. The number of teeth 
reckoned as laterals varies somewhat on different parts of the same 
radula, as I have observed in several species; so that the importance 
of variations from the counts of teeth given in the text must not be 
overestimated. Except in the case of A. chiricahuana, all of my prepa- 
rations of genitalia, jaws and radule are from specimens of the type 
lots. 
From the data now in hand, it seems in a high degree likely that the 
ancestral stock of all known Ashmunellas had a tridentate aperture. 
There was a tendency to split the basal tooth, perhaps not expressed 
in the original stock, but subsequently developed orthogenctically in 
most of the subgroups. This tendency culminates in the levettei group, 
where the original basal tooth has been divided into two distinct and 
often widely separated teeth. There has also been degeneration of the 
aperture-teeth, parallel in various stocks, and culminating in several 
toothless forms, astonishingly alike, though of undoubtedly diverse 
parentage. A. hyporhyssa Ckll., robusta Pils., chiricahuana Dall, esuri- 
tor Pils., ete., are convergent forms of this character. The true rela- 
tionships of such simplified species must be demonstrated by their 
internal anatomy. The idea that the toothless forms are primitive can: 
hardly be entertained in view of their anatomical diversity and their 
demonstrable relation to several groups of toothed species, the evi- 
dently homologous teeth of wnich, on this hypothesis, would have 
been independently evolved. This would be homoplasy on too 
extensive a scale to be readily believed. 
The aperture-teeth in Ashmunella curiously imitate those of Polygyra, 
a genus not in the least related. In Europe, /sognomostoma and Heli- 
codonta have evolved similar forms in still other phyla. 
There has been a tendency to overload Ashmunella with subspecifie 
names, which would logically end in naming every colony in existence. 
Ido not minimize the importance of noting and recording local differen- 
tiation. My appreciation of its omnipresence convinces me that it 
cannot all be stereotyped in nomenclature, and if it were, the result’ 
would be too unwieldy for any human intellect to make use of. 
