Maryland Geological Survey 425 



Occurrence. — Monmouth Formation. Brightseat, Prince George's 

 County. 



Collection. — Maryland Geological Survey. 



? ROSTELLITES JAMESBURGENSIS (Weller) 



Volutoderma jarnesburgensis Weller, 1907, Geol. Survey of New Jersey, 

 Pal., vol. iv, p. 777, pi. xci, figs. 22, 23. 



Description. — " Shell of medium size, the dimensions of the type 

 specimen being: Height 30 mm., maximum diameter 17 mm. A 7 olutions 

 about four in number, the spire of moderate height, apical angle about 58°. 

 Suture well defined ; just below the suture is a rounded ridge marked by 

 conspicuous oblique costae about 1 mm. apart on the outer volution ; just 

 below this ridge is a narrow, concave band, outside of which, upon the 

 shoulder of the volution, is a series of strong rounded nodes about 3 mm. 

 apart from center to center on the outer volution, which continue longitu- 

 dinally as strong, rounded ribs to the anterior extremity of the shell. Sur- 

 face also marked by fine vertical lines of growth ; revolving lines entirely 

 absent. The internal cast is similar in general form, the suture is well 

 defined, the volutions are flattened above, or even slightly concave, towards 

 the aperture, sloping down-ward to the line of maximum diameter beneath 

 the row of strong nodes on the exterior, below which the sides are nearly 

 vertical to the suture below, or m the body volution becoming concave 

 towards the anterior extremity. The vertical ribs are shown on the 

 internal casts, but are much weaker than upon the exterior of the shell." — 

 Weller, 1907. 



Type Locality. — Jamesburg, New Jersey. 



Weller makes no mention of any columellar plications, nor does he 

 give any reason for referring the species to Volutoderma. The Maryland 

 individuals which have been tentatively referred to R. jarnesburgensis are 

 all fragmentary and inconclusive, but the general outline and the character 

 of the sculpture certainly suggest Cythara quite as strongly as they do the 

 Volutes. 



Occurrence. — Monmouth Formation. ? Brightseat, Prince George's 

 County. 



