j|.\ini,\M) (;i:i)i.()(;i( \i, >i i;\'i:v 157 



ordci ASPIDOHRANCHIATA. 

 Sub.ndcr KHllMDOGLOSSA. 



l-amilv TKOCIIIDAH. 



Cciuis C.lHlUil.A Kisso. 



GiBBULA (;i,ANi)ri,A (Conrad). 



Plate XX IX, Fi--- -■■'• 



Monodoiita (jhiiidiilii Conrad, ISoO, Jour. Acad. Nut. Sci. I'liilii., vol. vi, pj). :il4, 220, 



pi. ix, lig. 1 5. 

 Monodonta ulanduhi II. C. Lea, 1848, Proc. Acad. Nat. 8ci. Pliila., vol. iv, p. 102. 

 Movodoiita ulandula Conrad, 1866, Smith. Misc. Coll. (200), p. 11. 

 Gibbula glandiila Clark, 180."i, Johns Hopkins Univ. Circ, vol. xv, p. .5. 

 Gibbula gland ula Clark, ISOO, Bull. 141, V. S. Geol. Survey, p. 72, pi. xiv, fig. h. 



Descripiioii. — "Shell conical, ^villl aljont four convex volutions; re- 

 volving striae fine, crowded and wrinkled; suture deeply impressed; right 

 lip toothed within at the base; margin entire. 



" The teeth or tubercles extend to the base of the columella of this 

 shell." Conrad,, 1830. 



Length, 8 mm.; Avidth, T mm. 



Occurrence. — Aquia For.matiox. Piscataway (Conrad). Potomac 

 Creek, Upper Marlboro. 



Collections. — Johns Hopkins University. ^Maryland Geological Survey, 

 Philadelphia Academy of Natural Sciences. 



Genus CALLIOSTOM.^ Swainson. 



Calliostoma sp. 



Description. — Two specimens of CalUostoma, both too imperfect either 

 to figure or to describe, were found in the Aquia formation. The one 

 from below Potomac Creek is part of the base of the body whorl. It 

 shows a strong basal carina, and revolving threads of various size, all, 

 slightly granulate. The fragment from Upper Marlboro does not show 

 the surface decoration, but has a deep groove in the middle of the whorl. 



Occurrence. — xAquia Foemation. Upper ]\Iarlboro, 2 miles below Po- 

 tomac Creek. 



Collection. — Marvland Geolooical Survey. 



