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-stride 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 lamellae 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 Gastrocoptincc. 



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., I. 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. 



