602 SYSTEMATIC PALEONTOLOGY 



Outside Distribution. Mataivan Formation. Merchantville clay marl, 

 Woodbury clay, Marshalltown clay marl, Wenonah sand, Xew Jersey. 

 Monmouth Formation. Navesink marl, New Jersey. Black Creel- for- 

 mation. North and South Carolina. Peedee Sand. North and South 

 Carolina. Eutaiv Formation (Tombigbee sand member). Exogyra i>on- 

 derosa zone, Mortoniceras subzone, Georgia; Russell County, Alabama. 

 Eipley Formation. Exogyra ponderosa zone, Union Springs. Alabama; 

 Booneville, Mississippi. Exogyra costata zone, Georgia; Eufaula, Ala- 

 bama ; east-central Mississippi ; Alcorn, Union and Tippah counties, Mis- 

 sissippi. Selma Chalk. Exogyra costata zone, east-central Mississippi. 

 Extreme top of zone, Pataula Creek, Georgia. 



LIMA SERRATA n. sp. 

 Plate XXXIV, Figs. 14, 15 



Description. Shell small, moderately inflated, ovate in outline, inequi- 

 lateral; anterior area obtusely angulated; posterior evenly rounded: base 

 line arcuate, somewhat obliquely produced in front; umbones moderately 

 gibbous orthogyrate, slightly posterior in position : external surface sculp- 

 tured with thirty-two primary costa? (in the unique type the summits 

 are acutely angulated and form with the ' more obtuse interradials a 

 sharply serrate profile) ; radials upon the posterior portion less angular; 

 the ten anterior costae rounded, over-run and minutely nodulated by the 

 incrementals ; minute secondary threadlets developed in the interspaces on 

 the posterior medial portion of the disk; posterior submargin devoid of 

 radial sculpture; incremental sculpture obsolete over the medial portion 

 of the shell and only feebly developed posteriorly; submargins not 

 impressed, auricles minute, the anterior more so than the posterior, tri- 

 gonal, their dorsal margins forming the straight hinge margin (unfor- 

 tunately the posterior auricle was lost in shipment to the artist) ; ligament 

 internal, lodged in a small but relatively very wide resilium directly 

 beneath the umbones ; hinge dentition not developed ; shell monomyarian, 

 .the single muscle scar subcircular, placed above and behind the medial 

 planes of the shell ; pallial line indistinct ; interior finely plicated even to 

 the umbonal region in harmony with the external ribbing. 



