INVERTEBRATE PALAEONTOLOGY. 569 



below, but not proportionally mucb enlarged, and without a well-defined 

 mesial angle; suture rather deeply impressed; surface very nearly smooth, 

 or only showing under a magnifier very faint lines of growth, which are 

 moderately sigmoid on the body-volution ; aperture narrow-subovate, being 

 somewhat obtusely angular above, and narrowly rounded and apparently a 

 little effuse or sinuous below. 



Length, about 0.65 inch ; breadth, 0.24 inch ; slopes of spire nearly 

 straight, with a divergence of about 25°. 



This little shell resembles somewhat the last, but 

 differs materially in having more convex whorls, a 

 deeper suture, and a differently-formed aperture and 

 body-volution. Our figure on plate 42 gives an incor- 

 rect outline of its aperture, and, consequently, the 

 annexed cut is added with the view of conveying a 



.. „ . . . „ . . Goniobasiel gracilenta. 



more accurate idea ot this part and some ot its other 



I Magnified to about one 



characters. Like most of the other species here and a half diameters, to 



show the form of the aper- 



referred to Goniobasis, this is only provisionally placed t ure, &c, more correctly 

 in that group, as no entire well-preserved specimens than the figure on plate 42. 

 of-it have yet been seen ; while traces of its obscure lines of growth show 

 by their curves, as indicated on the body-volution in the cut, that its outer 

 lip possessed rather more the prominence below, seen in Pleurocera. 

 Locality and position. — Same as last. 



Goniobasisl subtortiiosa, M & H. 



Plate 42, figs. 17, a, b. 



Melania sublortuosa, Meek and Hayden (1857), Proceed. Acad. Nat. Sci. Philad., IX, 136. 

 Goniobasw 1 subtortiiosa, Meek (I860), in Conrad's Smithsonian Check-List N. Am. Eocene Invertebrate 

 Fossils, 12. 



Shell conoid-screw-shaped, thin; spire rather low ; Fi § 



volutions about five, very convex, and strongly carinate 

 around the middle, increasing rather rapidly in size 



Goniobasisl sabtortuosa. 



from the apex; suture deep in consequence of the Fig. 76. Showing aperture, 

 prominence of the angular whorls ; surface with moder- Fi «- "' An oppo8ite view " 

 ately distinct lines of growth ; aperture rhombic-suboval, about as long as 

 wide. 



Length, 0.39 inch; breadth, 0.21 inch; slopes of spire nearly straight, 

 72 u. 



