300 SYSTEMATIC PALEONTOLOGY 



adjacent lateral short and the anterior hinge-margin in front of it grooved 

 for the edge of the opposite valve ; middle of the disk smooth, the beaks, 

 posterior dorsal area, and the portions of the disk near the basal margin 

 more or less concentrically striated ; interior with the pallial sinus rising 

 to a small angle under the umbo, then descending in a somewhat wavy 

 line to a point on the pallial line considerably short of the anterior adduc- 

 tor scar; in the left valve the sinus is not angulated above and extends 

 somewhat nearer the adductor; the interior is marked with some faint 

 radiations near the adductors, but no thickened ray appears. 



" There is some little difference in the proportional height in different 

 individuals, in the amount of inflation, and in the arcuation of the pos- 

 terior dorsal margin; the posterior fold, or ridge bounding the posterior 

 dorsal area, is not strongly marked. Compared with T. tenella Verrill, 

 this species is a heavier and higher shell, with the posterior end more 

 pointed and decurved. The dorsal margin of the right valve is not 

 grooved in T. tenella, and the adjacent lateral is longer than in T. du- 

 pliniana of the same size." Dali, 1900. 



Length, 12.5 mm. ; height, 8 mm. ; diameter, 4 mm. 



Occurrence. — Calvert Formation". Plum Point {fide Dall). 



Collection. — U. S. National Museum. 



Tellina (Angulus) umbra Dall, 

 Plate LXXIII, Fig. 2. 



Tellina [Angidus) umbra Dall, 1900, Trans. Waguer Free lust. Sci., vul. iii, pt. v, 

 p. 1033, pi. xlvi, flg. 13. 



Description. — " Shell small, solid, markedly flexuous, moderately con- 

 vex, inequilateral, nearly equivalve ; anterior end longer, rounded ; pos- 

 terior end shorter, attenuated, bluntly pointed; beaks incons|)icuous ; 

 whole surface covered with close-set, regular, even, concentric threads; 

 hinge normal, right anterior lateral short and stout, posterior lateral small 

 but prominent; pallial sinus long, slightly convex above, reaching to the 

 anterior ray (which is obviously thickened), nearly similar in both 

 valves, and wholly confluent below. 



" This species is nearest to T. syharitica Dall, but is a larger and less 

 slender shell, with a less angular posterior end. It is doubtless the pre- 

 cursor of that sf)ecies." Dall, 1900. 



