ORCULA. 129 



This form is one of the most remarkable of the genus Orcula. 

 Its morphologic peculiarity lies in the manifold combination 

 of the characters of two species, 0. dolium and 0. gularis. 

 Its relation to these can be interpreted as due to a secondary 

 mixture, or to the survival of an undifferentiated stock in this 

 part of the northern Dolomites, representing a stage at the 

 beginning of the evolution of the two species, which elsewhere 

 show no intergradatiou. The former hypothesis is more prob- 

 able, that is, that these forms are the progeny of an actual 

 mixture of the two species. It inhabits part of the upper 

 Austrian Alps, bounded on the west by the Traunsee and in 

 the east by the valley of the Enns. 



Orcula gularis (Rssm.). (Vol. 27, p. 13). Text-figs. 16, 17, 18. 



This species is confined to the eastern Alps; forms so 

 labelled from the Carpathians seen are nothing else than slen- 

 der forms of 0. dolium. ' ' True montane forms are before me 

 from few places. Those collected on the northern slopes of 

 the Duerrenstein near Lunz (lower Austria) in about 1500 

 meters afford average measurements of from 5.7 x 2.45 mm. ; 

 on the Grossen Buchstein in 1700-1800 meters, 5.8 x 2.5 mm. 

 The shells are in general somewhat thicker and more strongly 

 rib-striate, the folds of the aperture, especially the parietal, 

 weaker. This is forma 0. gularis oreina St. Zim. (fig. 19). 



Orcula gularis restituta (Westerl.) (Vol. 27, p. 14). Text- 

 figs. 21, 22. 



This form does not differ from 0. gularis proper in external 

 form or dimensions, — width 2.7 to 2.8 mm., length 6.3 to 6.5 

 mm. The columellar lamellae are of equal strength, lie rather 

 close together, and reach equally far, quite to the sharp edge 

 of the peristome. The palatal callus is mainly very delicate, 

 not rarely lacking entirely, but it is also often quite strongly 

 developed, and then shows, near its outside limit, a little 

 prominence, which however has nothing in common with the 

 rudiment of a palatal fold ; the latter being ivanting in all 

 cases (figs. 21, 22). St. Annatale south of the Loiblpasse, etc. 



