- 469 - 



vated, but are destroj-ed in all the specimens e::cmiine'''. In 

 ■harraonj,- "/ith •tl- _ _ , ': '^f the nenl -ot -re the posterior e-nd 



of the shell is sc " ; ' ' ; .e liin^ile and escutcheon are 



T/ider than in 0. ballista; the ' 'i.ial, '^he teeth entire, the 



pallial sinus small an". , th n ati-Tiictor scars r.^-^hr- n --i. 



Length of an average £peoi:.an uv.o, nei^^irG iiw'.S, diameter 14. u nm." 



"The Bov.-de- others ith the 



recent 0_. :':;'hia b^' -,.., " ' -d. Onl^- a comparisoi. i. ^ 



needed to prove their distiiietness. " (Dall, lOO?'). 



T:,-pe lo-'alj-^; .- -.cv". ., Jasiaiea, 



Shell - ■ um sise, well inflated, ov'"''f-e-t".'igonal; rnargin 



sharply excavate i. anteriorly,, posteriorly? almost straight; vm- 

 bones high and tumid; lunule sharpl;; define"',, striate-; esciat- 

 G'''''C?n broad, bounded b^' a v^^el 1 - ". e pr * , , ':•'•■ ated; sciilpture 



of fifteen to tv/enty-ty;o concentric ribs, all ericept those on the 

 tip of the umbo thickened and reflexed; along a radial line about 

 three-fourths of the distance from ^" 'iriorerd, the c'"'-'--? -^^ 



the ribs suddenly fle3:ed downward and ■>: ' lav er and thinner 

 anfl as such continuir^g to the (K.rina bounciing the escutcheon; ant- 

 erio"'^ly the ribs evaneseing-r.bruptly „ "-'■: ■distance from •f-''^^ in- 



cised line liputing the lumile, the edge of the ventral riba be- 

 ing, v/hen perfect, geiitly reflexed ; ventral base of the ribs ob- 

 scurely or obviously punctate; between the ribs incrementals 



