1915.] NATURAL SCIENCES OF PHILADELPHIA. 381 



whorls of the cone somewhat more sharply striate than the cylindric 

 portion, upon which the striae are very fine and close; typically about 

 90 fine, close striae on the penultimate whorl. The latter part of 

 the last whorl is slightly compressed and hais slightly coarser, sharper 

 striae. The aperture is carried very shortly free, is not calloused 

 within, and has a narrowly reflexed lip. Within the latter part of 

 the penultimate and first part of the last whorl there is a rather 

 stout, obtuse lamella on the axis. No lamellae on the upper or basal 

 walls of the cavity. 



Length 12, diam. 4 mm.; 12 whorls. 



Dragoon Mountains, south of Tweed Canyon, the types from 

 Station 7, the summit of a limestone ridge separating the head of 

 Cataract Gulch from the next canyon opening westward, south 

 of Tweed Canyon, No. 112,225, A. N. S. P., collected by Ferriss, 

 Pilsbry and Daniels, October, 1910. Also taken at Station 7, and 

 Stations 29 to 37 southward from Stations 7 and 8. 



H. millestriata is related to H. campestris, from which it differs by 

 having more numerous, finer striae, and by the absence of internal 

 lamellae on the parietal and basal walls of the cavity, in a long series 

 of shells opened. Its range is separated from that of H. campestris 

 by the ridge of eruptive rock which runs from Cochise stronghold 

 along the south side of Tweed Canyon westward to the mesa; no 

 Holospiras being found on this ridge, so far as we know. The isola- 

 tion of the two species seems, therefore, to be complete. The species 

 is quite constant in hundreds of shells collected from many colonies, 

 as noted below; but in two stations in small hills on the mesa east- 

 ward of Middlemarch Canyon there is notable variation. Further 

 study should be given to these small forms of the border between 

 mountain and plain. In over a hundred shells opened from all the 

 colonies, only one has a very weak trace of a superior lamella, all 

 others having only a stout axial lamella. 



The type locality. Station 7, is on the divide, a ridge above an 

 abandoned mine and cabin. It may be reached by ascending Cata- 

 ract Gulch from Tweed Canyon, but much more easily along the 

 mountains eastward, as the gulch is rather a neckbreaker. The 

 specimens are quite uniform in sculpture. Length up to 12.2 mm., 

 and very rarely as short as 9.3 mm., with 10 whorls. (PI. XV, figs. 

 3, 3a, 36). Out of twenty opened, one has a weak, hardl}^ perceptible 

 trace of the superior lamella, the others having the axial lamella 

 only. A series of 1000 or more was taken. It occurs under stones, 

 etc., in places where there is no shade. 



