AZECA. 291 



Berichte Mittheil. Freude Naturwiss. Wien, vi, 1850, p. 99, for 

 O. tridens Drap. Azeca Leach, GRAY, P. Z. S., 1847, p. 175. 



Shell long-ovate or subfusiform, smooth and glossy as is usual 

 in the family, composed of 6 to 8 nearly flat whorls, the last 

 swollen behind the outer and basal lips. Aperture ovate, the 

 outer lip excised or retracted in its upper third, then contracted 

 with blunt or slightly expanded edge, the lip-ends connected by 

 a callous cord across the parietal wall, rising into a small 

 triangular tooth near the upper angle of the mouth. Parietal 

 wall bearing a deeply entering parietal lamella, a small tubercle 

 above its outer end, and a small lamella at the root of the colu- 

 mella. Columella with a vertical white lamina, and a basal 

 tooth or stout lamella. Outer lip with a marginal tooth and 

 sometimes lower palatal and deeply placed denticles. The 

 exterior coloration, and soft parts of Azeca have been described 

 by Jeffreys, Moquin-Tandon and others, but no mention is made 

 of pedal grooves or a tail-pore. The soft anatomy, except jaw 

 and teeth, has not been described. 



Type A. menkeana goodalli. Distribution, central Europe and 

 England. 



Azeca contains a single well-marked recent species, with a 

 number of subspecies or local races, of which only one, A. m. 

 goodalli, has been adequately worked out. Some half dozen 

 others, diagnosed by French "nouvelle ecole" authors, require 

 further investigation. A. elongata Taylor seems to be a remark- 

 ably distinct species, yet it is known by only two specimens, 

 and may possibly be an abnormal form. According to Knight, 

 the name Azeca w r as taken from a town of the tribe of Judah. 

 It appears that Leach used various other oriental geographic 

 names for genera of shells without much regard for their fitness. 



There are several tertiary species beginning with the middle 

 eocene A. boettgeri. The earliest are allied to modern forms, 

 and throw but little light on the genesis of the genus, which 

 must have arisen very early. In the miocene a group of species 

 with small teeth appeared (A. monocraspedon and its allies), 

 representing either a collateral phylum or a branch with sim- 

 plified apertures. The fossil species known to me are as 

 follows : 



