

!>\ 





.inff mil rrntrul slopt* are 8elf-eX|'lanatoi \ tenuv 



nuil liijumrnt: An elastic, horm band, of variable length, serving to hold the 

 valves in ( i. .HI. -II. .iifi -ihuiN'd ir \ .m.tUy over the dorsal edges close behind 

 "i under tlu> beaks. Hut rarely preserved in fossil she I 



ii/iimm- This is generally of cartilaginou- c.inM^tency. ami 



..ft. -n I. ut a modification or extension of the external ligament. In the latter 







ease it lies along the i inner bonier of the hinge, where its presence 



ma\ be indicated by linear thickened supports which, in casts of the interior. 

 ma\ MMBflttlDM be OOnfbVIKlad with mi|>reion> of lateral teeth. (H'AifWA/). 

 \ true nit. TIKI! cartilage. n>-ii;illy occupying a small pit beneath the benk- 

 '>'. Ill .iii.l \ III. i- found in .Yn/-i//.. .mil many other types of the 



secondary ami more recent rocks, but is rather rare among paleozoic species. 



fig. in. Wtatrati*a Hingt Tgpet, Miuclet and Pallia! Imprtniont. 



1 an.l II. iiit<Ti.>r of a n k 'hi vml\v of Lyrvdeima major I'lnch. of thr natural nlze, and th- 

 ]rtiiiii "f the valve x 2: upper beds of tho Cincinnati ({"'"P "f Ohio. 



HI. hinge of a upecle* of A'uriiiaiwi, nhowinK Internal canilatte pit at r. 



I \ . t, . rlorof a left valve of Vatmxemia kay*ia*a Safford, sp.. frin th<- upp<-r Trenton liiii.~.!nn.- ,, 



inllnal t.i-ili: /. r. p>Mterif>r lateral teeth: a. a.. anUrlcir adductor, and 

 / <i ini|ir>-vs|nn-. ;,., palllal lln> j+ 



a left vahv of an unnamed variety M Bfmonfckia radiata Rail, p. 

 hN^pMBtaMWrfatelfOkrudotJ Ull. 1847.) f nun th.- lower bed* of the CloeionaU grot 



th.- |.tTii>r ;i(|.|ii.-t-.r impreMlon^p. a.) and the pallia! line an- nMwMr <li*tlnrt. 



VI. i -t f Lgrodetma major .- alw. I an<l II), shnwln. 

 MMCular lmprMlop In a very satisfactory manner: a. a , anU'Hor add > a., posterior addii. 

 li m.. two palm of pedal mu- 



VII. ini.Ti'.r of a shell with a trongly sinuate palliaJ line (*), and an internal ligament pit 

 Ltitrnria eUiptica Botay. Pliocene, Bhodus (one-half nat ta outline of i ! I In 



with Fig. 34. land II 



VIII. iHi.l.-t.-nnlned spooler '' I fnpipn 



This term .ii'|.iie- to the teeth in general, but more especially w ben 



these are nmner. -n- U |iial. a; in 



^v&f 



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