152 SYSTEMATIC PALEONTOLOGY 



Golleciions. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. ISTational Museum, Philadelphia Academy of Natural Sciences. 



Family CAPULIDAE. 



Genus CALYPTRAEA Lamarck. 



Calyptraea apeeta (Solander). ,■ 



Plate XXAail, Figs. 4, 5. 



Trochus apertus Solander, 1766, Foss. Haut., p. 9, figs. 1, 2. 



Calyptraea trochiformis Lamarck, 1804, Ann. Mus. d'Hist. Nat., voL i, p. 15, fig. 3. 

 Calyptraea trocMformis Clark, 1895, Johns Hopkins UniY. Circ, vol. xv, p. 4. 

 Calyptraea trocJiiformis Clark, 1896, Bull. 141, U. S. Geol. Snrvej-, p. 70. 

 Calyptraea aperta Harris, 1899, Bull. Amer. Pal., No. 11, p. 84, pi. xi, ligs. 13-16. 



Description.— '^h.eW orbicular, thin, obtusely conical; volutions three 

 or four; apex subcentral; later whorls spinose; whole surface (except 

 protoconch) roughened with irregular, wavy lines of growth, or a vermi- 

 cular shagreening; septum slightly concave; pillar reflected, giving the 

 appearance of an umbilicus. 



This species is represented, usually in a poorly preserved state, in 

 nearly all the beds and localities of the Maryland Eocene. The largest 

 specimens are in the Aquia formation. 



Length, 15 mm.; width, 28 mm. 



Occurrence. — IsTan-jemoy Foemation. Popes Creek, Woodstock, East 

 and west of Port Tobacco, ^ mile below Chapel Point. Aquia Forma- 

 tion. Fort Washington, Glymont, Clifton Beach, Liverpool Point, Up- 

 per Marlboro, Aquia Creek, Potomac Creek, 2 miles below Potomac 

 Creek, 1 mile southeast of Mason Springs. 



Collection. — Maryland Geological Survey. 



Family LITTORINIDAE. 



Genus LITIOPA Rang. 



Litiopa maeylandica n. sp. 



Plate XXVIII, Figs. 6, 6a. 



Pescn^^/to//.— Shell thin, with six wliorls; the first two wliorls smooth,, 

 the third witli fine, closely-set, revolving striations fi'om suture to su- 



