220 AULACOSPIRA. 



of the sinulus. All of these small accessory teeth are probably 

 variable in development. All of the teeth are minutely spinif- 

 erous, especially the smaller ones. 



The external sculpture resembles that of G. everetti, but the 

 spiral threads are not so conspicuous, though rather coarse, 

 and growth-striae are hardly noticeable. Figured from co- 

 types, one of which measures, alt. 1.8, greatest diam. 2.55 mm. 



It differs from G. everetti chiefly in the base, as indicated 

 by Mr. Fulton. Compare figs. 4 (everetti) and 7 (dohertyi). 



THE AULACOSPIRA AND SYSTENOSTOMA GROUP. 



The lamellas and folds, when least decadent (as in Aulaco- 

 spira azpeitiae), are unmistakably of Gastrocoptid type; but 

 in most of the species there has been more or less reduction of 

 the armature, terminating in toothless species. 



The last whorl often turns a little towards the axis, and 

 more or less downward. This contrasts with Boysidia and 

 Hypselostoma, in which there is more or less straightening of 

 the last whorl, which tends to a tangential direction, and in 

 the more evolved forms the aperture looks upward. This an- 

 tithesis appears to indicate that Hypselostoma and related 

 genera on the one hand, Aulacospira and Systenostoma on the 

 other, form two collateral phyletic series in the Gastrocoptin<z. 



The species are figured on plate 38. 



Genus AULACOSPIRA von Moellendorff. 



Aulacospira MLLDFF., Bericht Senck. Naturf. Ges. Frank- 

 furt a. M., 1890, p. 224. PILSBRY, Man. Conch., ix, p. 279, 

 type A. scalatella. Micropetasus MLLDFF., 1. c.; same type. 



The shell is helicoid, wider than high, small, umbilicate, of 

 thin, corneous texture, unicolored. Spire more or less conic, 

 subscalar and angular peripherally from the mucronate sum- 

 mit ; whorls 4 to 5, flattened or with a spiral concavity above 

 the angle, the last whorl sometimes rounded, often shortly 

 free in front, never straightened or ascending. Aperture 

 very oblique, rounded, with to 5 teeth within ; the peristome 

 thin, expanded. 



Type: A. scalatella. Distribution: Philippine Islands. 



