MARYLAND GEOLOGICAL SURVEY 383 



OSTREA Sp. 



In addition to the above described species of Ostrea some indetermi- 

 nate valves were obtained at Church Hill, Skipton, and three miles west 

 of Centerville. 



Superfamily PTERIACEA. 

 Family MELINID/E. 



Genus MELINA Retzius. 



Melina maxillata (Deshayes). 

 Plate CII, Fig. 3 ; Plate CIII, Fig. 1. 



Perna maxillata Lsima.rck, 1«19, An. sans Vert., vi, i, p. 143, (syn. excl.): ed. Deshayes, 



1836, vii, p. 78 (fide Dall). 

 Perna toria Say, 1820, Amer. Jour. Sci., vol. ii, p. 38. 



Perna maxillata Conrad, 1840, Fossils of the Medial Tertiaiy, p. 52, pi. xxvii, fig. 1. 

 Isognomon torta Conrad, 18f>3, Proe. Acad. Nat. Sci. Phila., vol. xiv, p. 579. 

 Melina torta Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 6. 

 Perna torta Whitfield, 1894, Mou. xxiv, U. S. Geol. Survey, p. 36, pi. v, figs. 12, 13. 

 Melina maxillata Dall, 1898, Trans. Wagner Free Inst. Sci., vol. iii, pt. iv, p. 667. 



Description. — Shell angularly pointed and slightly curved anteriorly, 

 posteriorly ovate, surface moderately convex, with irregular shallow con- 

 centric undulations marking growth lines; ventral edge thickened and 

 somewhat inrolled; ligament area broad with fifteen to twenty shallow 

 transverse grooves; exterior covered by a thin prismatic layer, interior 

 layer pearly, thick, composed of many thin shelly laminae, interior surface 

 nacreous. 



This shell is very rarely obtained entire. The prismatic layer is 

 almost always gone entirely, and of the shelly, pearly portion, only the 

 heavy anterior part is usually preserved. The shell is very often bored 

 by Martesia ovalis and other burrowing forms. Perfect valves are very 

 rare but may l^e obtained at Plum Point, Jones Wharf or Pawpaw Point 

 at water level. 



Length, 165 mm.; width, 90 mm.; diameter, 17 mm., though frag- 

 ments of larger individuals are often found. 



Occurrence. — St. Mary's Formation (?). Cove Point (?). Chop- 

 tank Formation. Governor Eun, Jones Wharf, Pawpaw Point, Dover 

 Bridge, Greensboro, Cordova, Skipton, St. Leonard Creek, Calvert 



