MICROPHYSA. 173 



attachment, beyond which projects slightly the long, distinct cutting point. 

 Laterals like the centrals, but asymmetrical by the suppression of the inner 

 lower angle of the base of attachment, and inner side cusp and cutting point. 

 Marginals (C) aculeate, their bases of attachment less sole-like than in Zonites, 

 but more circular in outline. Fig. C shows these bases of attachment. Fig. 

 D gives one marginal tooth in profile. 



This is the first known instance of a species with ribs on its jaw having 

 aculeate marginal teeth, or of a species furnished with a Zonites-Yike shell hav- 

 ing decided ribs upon the jaw. It will be difficult to find a place for the species 

 under any description of genus or subfamily. The shell is that of Zonites, but 

 that genus has a ribless jaw with median projection. It will be seen that its 

 ribbed jaw and aculeate marginal teeth do not sustain my assertion (p. 47) 

 that for the larger divisions these organs may be relied on as systematic char- 

 acters. The result of my examination of this species was as unexpected as it 

 is puzzling. 



Microphysa Ingersolli, BLAND. 



Shell 1 umbilicated, discoidal, thin, translucid, nearly smooth, white; spire 

 flat, summit subimmersed ; suture impressed ; whorls 5^, rather convex, slowly 

 increasing, the last not descending, more convex below Fi 



the periphery ; breadth of umbilicus nearly 1 mill. ; 

 aperture subvertical, higher than broad, lunate ; peri- 

 stome simple, acute, margins remote, columellar margin 

 slightly reflexed, basal margin subsinuate. Greater 

 diameter 4, lesser 3| mill. ; height, 2| mill. (Bland.) 



Helix Ingersollii, BLAND, Ann. Lye. Nat. Hist, of N. Y., 

 XI. 151, Fig. (1874). INGERSOLL, Special Rep. on 

 Recent Moll, of Colorado, ed. 2, 1876, p. 397. 



A species of the Central Province. Howardsville, 

 Baker's Park, 9,300 feet above the sea, abundant in wet 

 places on the mountains : not uncommon at Cunningham 



Microphyta Ingersolli, 



Gulch, near the former locality, clinging to the almost enlarged, 



vertical face of a trachyte cliff, at an elevation of about 11,000 feet; the finest 

 specimens came from this spot ; found also on the southern slope of the Sa- 

 guache Mountains, in the Las Animas and La Plata Valleys, in the same sta- 

 tions as affected by Succinea. All the localities mentioned are in the south- 

 western corner of Colorado. 



l T. umbilicata, discoidea, tennis, translucida, sublevis, alba ; spira plana, vertica sub- 

 immersa ; sutura impressa ; anfr. 5, convexinsculi, lente acrescentes, ultimus non descen- 

 dens, infra peripheriain convexior ; umbilicus fere 1 mill, latus ; apertura subverticalis, 

 altior quam lata, lunaris ; perist. simplex, acutum, margiuibus.remotis, columellari bre- 

 vissime patente, basali subsiuuato. 



