AULACOSPIRA. 221 



This group was formerly thought to belong to the Helicida?. 

 It has apertural dentition entirely of the Gastrocoptid type. 

 The teeth, by their forms and positions, are clearly homologous 

 with those of Hypselostoma, Gastrocopta and allied genera, 

 and unlike those found in Helicidcc. The genus undoubtedly 

 belongs to the Pupillidcc, in the subfamily Gastrocoptince. 



Characters in common with Hypselostoma are the angular 

 whorls, more or less sulcate above the angle ; the delicate, hair- 

 like spiral strias, the texture of the shell and the open um- 

 bilicus. Conspicuous differential features are the rather de- 

 scending instead of ascending last whorl, which does not be- 

 come straightened in its latter part, and the downward-look- 

 ing, instead of vertical or upturned aperture. 



The teeth are more or less decadent in most of the species. 

 A. azpeitiae, in which they are well developed, often shows a 

 distinct though small angular lamella joined to the anterior 

 end of the parietal (pi. 38, fig. 17). It has also a columellar 

 lamella, upper and lower palatal and basal plica?, in the 

 typical positions. 



The minute spiral stria? were not mentioned in the original 

 descriptions, but I find them on all of the species except A. 

 triptycha, which I have not seen. 



Key to Species of Aulacospira. 



a. Angle of the last whorl continuing to the aperture ; peri- 

 storne continuous and free (Aulacospira, s. sir.}. 



&. Aperture toothless; shell very much depressed, alt. 

 1, diam. 3.2 mm. Cebu. A. mucronata, no. 1. 



6 1 . Aperture with 1 to 5 teeth; shell less depressed. 



c. Trochiform, the spire conic ; umbilicus scarcely 

 one-sixth the diameter; an obtuse columellar 

 and sometimes the trace of a parietal lamella. 

 Cebu. A. hololoma, no. 2. 



c 1 . Shell more depressed ; umbilicus wider, con- 

 tained 4 to 41/2 times in diam. 



d. An obtuse, low, columellar lamella and 

 sometimes the trace of a parietal; alt. 

 1.55 to 1.75, diam. 3.1 mm. Ilin, near 

 Mindoro. A. porrccta, no. 3. 



