a „ ^. -, LAMELLIBRANCHIATA. 625 



Saffordia.l 



the margin is rounded in S. striatum. The four or five Cincinnati species known to 

 me are all much higher posteriorly. 



Formation and locality.— Middle Galena, Goodhue county, Minnesota. The exact locality is about 

 thirteen miles south of Cannon Falls. 



Genus SAFFORDIA, n. gen. 



Shell rather small, transversely subovate, moderately convex, equi valve, very 

 inequilateral; back arcuate, beaks anterior, not large, curving obliquely inward and 

 forward; umbonal ridge moderate; between the ridge and the dorsal edge a more or 

 less distinct sulcus. A sharply defined lunule beneath the approximate beaks, while 

 posterior to them there extends to the extremity of the hinge an equally distinct 

 escutcheon. Hinge plate thin, arcuate, with one horizontal wedge-shaped cardinal 

 tooth in the left valve which entered into a corresponding cavity in the under side 

 of the hinge plate of the right valve immediately behind the beak. Posterior half 

 of hinge consisting of a slender lateral tooth in the left valve and a corresponding 

 furrow in the right. Anterior to the center an elongate depression for the reception 

 of an internal ligament. Anterior muscular scar distinct, deep, subcircular, situated 

 beneath the lunule; pallial line sim'ple, submarginal, posterior scar undetermined. 

 Test rather thick in the anterior part. 



Type: S. ventralis, n. sp. 



Beside the type, the Hudson River strata of Fillmore county, Minnesota, contain 

 another species having the characters ascribed to this genus. This I published 

 recently as a new species of Cuneamya, giving it the specific name sulcodorsata . It 

 is a more elongate shell but otherwise closely related to S. ventralis. A third species, 

 this one from the Galena, I described from casts of the interior as Cypricardites ? 

 modestus. 



The position of Saffordia seems to be near the Devonian Grammysia, the hinge 

 being similar in the two genera, though not by any means identical. In Grammysia 

 namely, as is shown in Hall's work on the Devonian Lamellibranchiata (Pal. New 

 York, vol. V, part i, plate lviii, fig. 6), there is no cardinal tooth in the left valve as in 

 Saffordia, nor ai-e the slender posterior lateral teeth represented. Another dis- 

 tinguishing feature of the latter, and one that is common to many Lower Silurian 

 shells, is found in the greater depth of the anterior muscular scar. In the genus 

 Cuneamya the hinge, aside from the escutcheon, is quite different, the test is very 

 thin, and the muscular impressions exceedingly faint, while the back, instead of 

 being arcuate, is concave behind the beaks, the latter being also tumid and much 

 more prominent. 



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