MARYLAND GEOLOGICAL SURVEY 607 



Paranomia lineata Conrad is separated from P. scabra (Morton) Con- 

 rad by the regularly ovate outline and its coarser, more prominent and 

 more distant radials. All of the specimens observed have been a little 

 smaller than the adult P. scabra, but this may have been due only to the 

 fortunes of collecting. 



Occurrence. MATAWAN FORMATION. One mile east of the Maryland- 

 Delaware Line, Chesapeake and Delaware Canal, Delaware. 



Collections. Maryland Geological Survey, Philadelphia Academy of 

 Natural Sciences, New Jersey Geological Survey, U. S. National Museum. 



Outside Distribution. Monmouth Formation. Navesink marl, New 

 Jersey. ? Ripley Formation. Tennessee. 



Genus ANOMIA (Linne) Miiller 

 [Prodr. Zool. Dan., 1776, pp. xxxi, 248] 



Type. Anomia ephippium Linne. 



Shell inequivalve, adherent, generally subcircular or oblong; left valve 

 more or less convex, right valve flattened ; hinge margin of left valve often 

 incurved and slightly thickened; ligament scar found directly beneath 

 left umbone ; interior of disk of left valve scarred with an adductor and a 

 major and minor byssal impression, the major byssal scar being the largest 

 of the three and dorsal to the adductor and minor byssal scars which are 

 usually subequal; interior of right valve containing foraminal opening 

 and, ventral to it, the impression of the adductor muscle ; posterior dorsal 

 margin of right valve carrying inconspicuous ligamental process ; pallial 

 line simple. 



" The fossil species of this group are very difficult things to study, since 

 the lower valve is seldom preserved and the muscular impressions can 

 seldom be made out. . . . To the natural difficulties is added that due to 

 the fact that the sculpture in this genus is very variable in perfectly normal 

 specimens and is further complicated by the differences of form and sur- 

 face, due to the object upon which they are sessile. I have satisfied myself 

 by the examination of a large number of recent specimens belonging to a 

 single species from a single locality that the relative positions of the 



Etymology: dvoyueuos unequal, unlike. 



