264 SYSTEMATIC PALEONTOLOGY 



Description. — " Shell orbicular, flattened above, smooth, margin 

 rounded; substance of the shell rather thin; spire nearly concealed; outer 

 lip sharp; callus impressed in the centre, bounded by a fine impressed 

 line; mouth nearly round." Lea, 1833. 



This species may be readily distinguished from the other Teinostomas 

 of the Maryland Miocene by its smooth, highly-polished shell, and by the 

 thick smooth callus which fills the umbilicus and which is bounded by a 

 faint impressed revolving line. 



Height, 1 mm. ; maximum diameter, 2 mm. 



Occurrence. — St. Mary's Formation. St. Mary's Eiver, Cove Point. 



Collections. — Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, Cornell University. 



Teinostoma calvertense n. sp. 

 Plate LXII, Figs. 3a, 3b, 3c. 



Description. — Shell small, solid, much depressed; body whorl large, 

 gently convex on top ; spire small, domed ; umbilicus small ; mouth round ; 

 surface marked by rather strong, somewhat irregular lines of growth. 



This species resembles T. nanum more closely than it does any other 

 Maryland species. It differs from nanum in having an open umbilicus 

 and in being much more depressed. 



Height, 0.5 mm.; diameter, 1.5 mm. 



Occurrence. — Choptank Formation, Jones Wharf, Governor Run, 

 Calvert Formation. Plum Point, Church Hill. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Teinostoma liparum (H. C. Lea). 

 Plate LXII, Figs. 4a, 4b, 4c. 



DelpMnula lipara H. C. Lea, 1848, New Fossil Shells from the Tertiary of Virginia, 



Abst., p. 9. 

 Belphinula lipara H. C. Lea, 1845, Trans. Amer. Philos. Soc, vol. ix, p. 261, pi. 



xxxvi, flg. 71. 



Description. — '' Shell orbicular, depressed, somewhat fiattened, rather 

 thick, smooth, shining; spire very short, rounded; sutures impressed; 

 whorls five, convex, polished ; last whorl rounded ; base smooth ; umbilicus 

 very wide, deep; mouth round." Lea, 1845. 



Height, 1 mm. ; maximum diameter^ 3 mm. 



