503 - 



pared — • -"-"'^ '-- .^ •- -^-^ - ,^. ri-'ht; valve of involut.- 



lamellar and there is a tendency for tv;o or three radial scries of 

 foliations to "be developed toviT.rd the posterior marp-i . ■ attach- 



ed valves have an ohvionsly different shape and sciilpiiu-e. -he 

 attached valve, usually the left, of 0, chi-oolana Os.ll (l) , from 

 the Tamps silez, Ohipola and Oak 'Jrove horizons, has more numerous 

 radials and Ilu. ur aoLi^vii^ '.-Idle on th: free valve tl-.e coii^eiitric 



fl). idem, p. 17-^8, nl, 56, fip-s. 19, 20. 



sculpture is S"presserl. ■, Tampa silex form, 2.* t.^:mpa8nsis ■''l~-11 (2) 



{2), idem, pp. 1598-1599, pi. 54, fi-. 6. 



ic also attached hy the left valve, on v/hich arc irre ' concen- 

 tric lamellae, \^ile on the right valve the lamcllce are "rr, 

 as in i^ivol uta. hut, excer)t for the occasioral presence of a few 

 oor..olote crenixlations on the marginal lamellfie, they are not crenu- 

 lated. 



The Santo Domingian " maercohylla " is a. heteroj-eneous assemhl- 

 age; som.e a-narently are ferrahle to the recent s-^eei , ' i"" e oth?rt 

 ■^re so eloce to involuta that they ;orooaoly choul ' he iiicluded luider 

 that species. 



