CHORISTES-HOMALOGYRA. 399 



smooth; whorls 4-5, very convex, with deep suture; lip simple, 

 everted partially over the umbilicus. Length, 6 mill. 



Off Martha's Vineyard, Mass.', 255 fms. 



Recent specimens agree well in form and structure with the above 

 named Canadian post-pliocene fossil; they are, however, somewhat 

 larger, and thinner, and Yerrill has accordingly given them the 

 varietal name of TENERA. 



Family HOMALOGYRID^. 

 Genus HOMALOGYRA, Jeffreys. 1867. 



H. ATOMUS, Phil. PL 61, figs. 4-6. 



Discoidal, planorbiform, very widely umbilicated, spire depressed 

 rather thin, semipellucid, smooth, slightly arcuately striate, some- 

 what shining; whorls 4, convex, rapidly enlarging, with deep suture; 

 lip thin, simple. Dium. 1 mill. 



Europe. 



It is Skenea niiidissima, Forbes imd Henley, H. simplex, Costa, 

 vars. pailida and polyzona, Brusiuu, and Var. vitrea, Duprey. 



H. ROTA, Forbes and Hanley. PI. 61 fig. 7. 



Discoidal, flat above and concave below, very smooth, subpellucid, 

 shining, with short radiating ribs above and below, enlarging and 

 curving from the sutural line, and not extending to the periphery, 

 whorls 3, convex, with deep suture. Diam. 5 mill. 



Europe. 



H. pulchella, and H. paucicostata Costa, and Adeorbis costatus, 

 Weink. are synonyms. 



H. FISCHERIAXA, Monts. PL 61, figs. 8, 9. 



Planorbiform, discoidal, fulvous, Avith three spiral brown lines ; 

 whorls 4, with slight, numerous, incremental striae. 



Diam. 1 mill. 



Mediterranean Sea. 

 H. DENSICOSTATA, Jeffreys. PL 61, figs. 10, 11. 



Planorbiform, semitransparent, glossy, nearly flat above, concave 

 below, with close-set incremental striae, finally becoming microscopic; 

 whorls 4, rapidly increasing, the last one with a central carina on 

 the upper and lower surfaces, and another on the periphery; suture 

 narrow, but excavated. Diam. 1*87-3 mill. 



Off Newfoundland, K522 tins! Cape 7/<///r,v/. s JV. C. 7-17 fms. 



The last locality is for Skenea trilu-, Bush, which appears to me 

 to be a better grown condition of Jeffreys' species. 



