CIIORISTES-nOMALOGYRA. 399 



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

 everted partially over the umbilicus. Length, 6 mill. 



Of 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 Verrill has accordingly given them the 



varietal name of tenera. 



Family HOMALOGYRID^. 

 Genus HOMALOGYRA, Jeffreys. 1867. 



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



Discoidal, planorliiform, very widely umbilicated, spire depressed 

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

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

 lip thin, simple. Diam. 1 mill. 



Europe. 



It is Skenea nitidissima, Forbes Bud Hanley, If. simplex, Costa, 

 vars. pallida and polijzona, Brusina, 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. j)aucicostata Costa, and Adeorhis costatus, 

 Weink. are synonyms. 



H. FiscHERiANA, Mouts. PL 61, figs. 8, 9. 



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

 whorls 4, with slight, numerous, incremental strife. 



Diam. 1 mill. 



Mediterranean Sea. 

 H. DENSicosTATA, Jcflfrcys. PI. 61, figs. 10, 11. 



Planorbiform, semitrausparent, glossy, nearly flat above, concave 

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

 whorls 4, ra})idly increasing, the last one with a central carina on 

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

 narrow, but excavated. Diam. l"87-3 mill. 



Off XnvfoKiidland, 1622 fms! Capf:' Hatter as, X. C. 7-17 fms. 



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

 to be a better grown condition of Jeffreys' species. 



