- 405 _ 



middle of the shell are slightlj" ijarrower a-nd sharper than those 

 on eithp"-'" f^w^ . '^he intprp'^oe hetv/een ''"''■ '^ i - -•- ^ oosteriorly ^ ■■^•^ 

 the anterior ribs, on whioh the nodules are Oi- the anterior side, 

 and the first of the n ribs v.'hieh bear the norlules across 



their entire ridth, tp-^'JR '-o >■'- ^^tT-'^tl^ ..: . _ ^ _ .e;.er '-han 



those ad^'oin:" , On ^oung shells the lov/ posterior portion of 

 the ten posterior ribs is usually obsolete, so t::at the nodules 

 re st in th ^ ^ ^^t "^ ■"• p "oace s * 



1. bov- dene use is recog-nized by its sniall size, soraeTrhat in- 

 eouilateral shape aiai numerous nodulated ribs. The raost closely 

 related form is ■^'-" recent Jest Indian _0. auric at -jjh linnaeus (I), 

 but, besides the differences po ' out in '■' - - -otation, tr.e 



'D. Z'.Bt. ITat,, ed, IC, p. CZO^ 1758; P.eeve, '^onch. Icon. , ' ^'ol . 

 2, Oardiu-m . pi. G, fig. 33, 1844. 



Bov.'den speci-iens have more rounded nodules and none of the ribs 

 bear two rovrs of nodules Y/Mle in nun- ica turn one to four ribs 



ir'.ime''^iately succeedini? the anterio"" -^^'^ ' ■' -■--- ,- ..oi-ir- .",^ixbly nodul- 

 ated. The above t^-o species, the Vicksburf;;:ien 2.* precarsor 

 Jail (£), Ghipolan 0. viril e Call (") an-1 O. '^aT^ile 'Dall (4), 



f.M. loc. cit., p. 108G, pi. l-S, fig. 10, 1900. 

 f'^^. loc. eit., p. 1086, pi. 48, f 1: . 1, 1000. 

 (4). loc. ci^., p. 108C, pi. 48, fi^. 17, 1900. 



