28 Palaeontographica Americana 28 



Area ponderosa Say 

 Plate VI, Figures 6, 7, 8, 9, 10 



Area ponderosa Say, Acad. Nat. Sci. Phila., Journ., ist. ser., vol. 2, p. 267, 1822. 



Area contraria Reeve, Conch. Icon., Area no. 55, 1844. 



Area elegansV)a\\.,Z€\\.sc\ir. Mai., 1847, P- 92 (^"'(^ Dall). Not .,4. f/(?g-a«j Perry, Conchology, 



pi. 60, fig. I, iSii; A. elegans Roemer, 1836; A. elcgans d'Orbigny, 1844; A. elegans Wood, 



1846, or A. elegans de Koninck. 

 Noelia ponderosa H. and A. Adams, Gen. Rec. Moll., vol. 2, p. 537, 1S58. 

 Area {Noetia) ponderosa Dall, Wagner Free Inst. Sci., Trans., vol. 3, pt. 4, pp. 617, 632, 633, 659, 



1898. 



"Shell somewhat oblique, very thick and ponderous, with from 25-28 ribs, each 

 marked by an impressed line; interstitial spaces equal to the width of the ribs; umbones 

 very prominent ; apices remote from each other, and opposite to the middle of the hinge, 

 spaces between them with longitudinal lines as prominent as their corresponding teeth; 

 anterior margin cordate, flattened, distinguished from the disk by an abrupt angular 

 ridge; posterior edge rounded, very short; inferior edge nearly rectilinear, or contracted 

 in the middle * * *." — Say, 1822. 



In the original description anterior and posterior are reversed. 



Ribs twenty-five to thirty-two; width of ribs and interspaces not varying much on 

 the different parts of the shell; ribs with a mesial sulcus, sometimes with two sulci; a 

 fine interstitial rib in each interspace, more prominent on the umbonal ridge and some- 

 times indistinct on other parts of the shell; ribs and interspaces crossed by fine, evenly 

 spaced, concentric lines which are stronger in the interspaces; umbonal ridge angular, 

 posterior end produced, posterior margin nearly straight; muscle scars with an elevated 

 border; anterior margin of cardinal area elevated; ligament area longer anteriorly and 

 bounded posteriorly by a narrow uncovered strip extending diagonally backward from 

 the beaks; transverse grooves in the ligament stronger anteriorly; line of teeth curved at 

 the ends, central teeth fine and vertical, anterior teeth larger and v-shaped, posterior 

 teeth large and oblique with smaller, v-shaped teeth toward the center of the line; epi- 

 dermis brownish black. 



This is a variable species. Specimens from the Pleistocene of Louisiana and South 

 Carolina are mostly short and high like some recent shells from Ft. Barrance, Florida. 

 A valve from the Pliocene of the Croatan beds is unusually long, low and flat, and an- 

 other from the same beds is unusually large, 71 mm. long and 61 mm. high. Neither of 

 these can be placed in the species limula which is present in the same beds. 



It is apparent that Reeve's A. contraria is the same as Say's species. Dall places 

 A. elegans in synonymy with A. ponderosa and says, "There can be little or no doubt 

 that the names of Reeve and Philippi are based on young specimens of this somewhat 

 variable shell." This is one of the best known of the recent Areas and is easily recog- 

 nized by its heavy shell, interstitial ribs and twisted appearance. 



Dimenst07is (long form). — Lon.+2S,-3i; alt. +9,-34; diam. 40 mm. 



Occurrence. — Pleistocene of Cape May and Atlantic City, New Jersey; of Maryland, 

 near Cornfield Harbor, at Wailes Bltoff, on the Potomac River; of Simmons Bluft", South 

 Carolina; and many points on the coast of Florida; recent on the eastern coasts of North 



