A-RT.22 MITEOSPIEA, A XEW GASTEROPOD KIRK 5 



directly underlies a fauna which seems to correlate closely with 

 zone N of the Chazyan section of Canada. Specimens have been col- 

 lected in the Las Vegas quadrangle, southern Nevada; Inyo and 

 Panamint Ranges, Calif.; and Toyquima, Monitor, and Antelope 

 Ranges of central Nevada. 



Types. — The cotypes are in the collections of the United States 

 National Museum No. 80840, 80847, 80848. The specimens from the 

 Las Vegas quadrangle were collected by C. R. Longwell. Those from 

 the Toyquima and Monitor Ranges were collected by Edwin Kirk. 

 Specimen, Figures 1, 2, Plate 1, and Figures 1, 2, Plate 2, specimen, 

 Figure 3, Plate 1, and specimen. Figure 5, Plate 3, were collected 

 in the Las Vegas quadrangle, Nevada, by Prof. C. R. Longwell. The 

 •exact locality is " Summit on Alamo road south of Sheep Playa. 

 Outcrops just west of summit." Specimen, Figure 4, Plate 3, was col- 

 lected by Edwin Kirk on the east front of the Toyquima (Toiquima) 

 Range, Nev., near the mouth of a canyon variously known as Ike's 

 or McMonigle's. This is in the Lowry Peak quadrangle. Specimen, 

 Figures 1, 2, 3, Plate 3, was collected by Edwin Kirk on the east 

 front of the Monitor Range facing Antelope Valley about 5 miles 

 south of the mouth of Ryegrass Canyon, Lowry Peak quadrangle, 

 Nevada. 



EXPLANATION OF PLATES 



Plate 1 



Mitrospira longiveUi, new genus and species 



Figure 1. Lateml view of large specimen. The growth lines to the right near 

 the aperture are abnormally developed and probably indicate a 

 gerontic individual. The apparent angulation at the periphei-y of 

 the last whorl is due to weathering. 



2. Lateral apertural view of same specimen. 



3. Vertical section. The apex of the spire has been removed by weather- 



ing. Note the progressive filling of the living chamber by sec- 

 ondary deposits of lime. The interruption in the last whorl, to 

 the left, is due to the fact that the section cuts through the aper- 

 tural notch. 



Plate 2 



Mitrospira lonffwelU, new genus and species 



FiGUKE 1. Upper view of same specimen shown in Plate 1, Figures 1, 2, show- 

 ing the wide umbilicus. 

 2. Lower, apical view of same specimen. 



