MARYLAND GEOLOGICAL SURVEY 24? 



Description. — " Subovate, depressed ; apex prominent ; one side with 

 squamose lines, the opposite with finer ramose lines destitute of scales; 

 diaphragm contracted.'' Conrad, 1842. 



Height, 7 mm. ; length, 30 mm. ; width, 25 mm. 



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

 2 miles south of Governor Eun, Flag Pond, Dover Bridge, Greensboro. 



Collections. — Maryland Geological Survey, Johns Hopkins University. 



Genus CALYPTR/^A Lamarck. 



Calyptr^a aperta (Solander). 

 Plate LIX, Fig. 1. 



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



Calyptrcea trochiformis Lamarck, 1804, Ann. Mus. d'Hist. Nat.,voL i, p. 385, pL xy, 



fig. 3. 

 ? Tnfundibnliim gyrinum Conrad, 1834, Jour. Acad. Nat. Sci. Phila., voL vii, 1st 



ser., p. 134. 

 Infundihidum perarmatum Conrad, 1841, Proc. Acad. Nat. Sci. Phila., vol. i, p. 31. 

 InfuncUbulum perarmatum Conrad, 1843, Jour. Acad. Nat. Sci. Phila., vol. viii, 1st 



ser., p. 186. 

 Infundihidum perarmatum Conrad, 1843, Proc. Nat. Inst., Bull, ii, p. 182. 

 Infundibulum perarmatum Conrad, 1845, Fossils of the Medial Tertiary, No. 3, p. 



80, pi. xlv, tig. 6. 

 Trochita perarmata Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 569. 

 Trochita perarmata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 15. 

 Calyptriea trochiformis Dall, 1892, Trans. Wagner Free Inst. Sci., vol. iii, pt. ii, 



p. 353. 

 Infundibulum perarmatum Harris, 1893, Amer. Jour. Sci., ser. iii, vol. xlv, pp. 24, 35. 

 Trochita perarmata Whitfield, 1894, Mon. xxiv, U. S. Geol. Survey, p. 124, pi. 



xxii, figs. 15-19. 



Description. — "Trochus {apertus) testa gibboso-conica exasperata 

 obliquata subtus concava, apertura augustata. 



" Primo intuitu Patellis assimilatur illisque quae Lahio interno in- 

 structs sunt, cfr. Linn. Syst. nat. n. 654-658. Specimina auteni perfecta 

 spirant ostendunt completam, aufractus licet pauciores quam in con- 

 generibus; Apertura etjam magis contracta est. 



"Testa magnitudine Juglandis sed depressior, ssepeque minor; tabula? 

 imposita conum formans gibbosiusculum, quo etjam a congeneribus dif- 

 fert; externe scabra, subtus loBvis, concava. 



"Apertura augustata, lateribus magis roduntatis quam in reliquis hujus 

 generis." Solander, 1766. 



