

with a minute beak and a rounded. m>-.-ial fnld. ami a narrow -ub-lim-ar area. I'licati'.n- 

 obscure, becoming obsolete toward- tin- cardinal anje-. ami dyim_r away in the m-L'hbourl. 

 nf the himje-line. Surface marked with shallow mneentrie furrnw- -ep-Tited by int. I 

 which an.- .-ruddetl with elongated tubercle-. Tin-re an- IV- mi tin-.-.- in t'. Mir r in .re furrows 

 in the -|iacu of two lines 1 , ami fmm five \<i .-i'_ r ht elnn-ated tubercle- in ih,- -pai. ..... f I<H> line 



tran>verselv. In easts of the exterior. tin- . inn-ated tubercle, are repre-ented bv narrow 



elongated pits arranged LU concentric bands. 



,^i /in/>ri"/<i not uncommonly attains a width of an ineh ami thre.- .jirirt. r 



length of thirteen line-, but a-. xample- are -mailer than tin-. It i- ivadih 



by its comparatively short hinue-line, it- rounded cardinal an-lc-. it- nK-cun- plication. and 

 -urface ornamentation. 



/. ' \ty and Formation, Corniferoas Lime-tone of 1'm-t d.lhorne. Also, according to 

 Mr. Billini:-. in the Hamilton Shales of Bo-am|Uet. 



CviiTIVA (l>avidson). 



Shell small and resembling that of Spirifera in i'- _ 'm ral form. Shell-structure punc- 

 tate. Valves very unequal; the ventral valve elevated and pyramidal in >hape ; tin- ar- 

 lii_h, with a Inn- narrow foramen, clo-ed Ly a p- u<l> deltidium : tli' 1 dental lamella- coin 

 in- from the mar-ius of the foraim n. and uniting t . form a nn-.-ial plate nr .-eptum, wl.ieh 

 divide- ill-- cavity uf the ventral valve into t\\n eninpartment-. !>.<r-al valvi- nearly Hat ..r 

 moderately convex. Spires well devl"ped. and resembling those ol and .\ 



The j'-nus G\ rtiti i-el..-ely allied t.. lialman/. and >'/> i I )'( >rhi'_'iiy . and 



ha- al-n near relation-hip with the u'-nu- Spi Two species have b.-.-n record,,! (,y Mr. 



I'.illitrj-. a- "eeurrim_ r in the Devonian Rockfl "f \\'i--(i-ni Ontario, namely ' 

 Hall .. from the (.'nrnit'T, MI- Lim---tnne. and t './///!> < 1 1 all i. frnin the Bamilton group. 



The latt'-r i- a i-nmrnmi .-peeies. hut the few example- of Cyr/tTUZ, which I ha\e -ecu from 

 CorniferOUB Lim'-to&o are tno imperfect to admit n| -peeitie determimitinii. 4 



101. ('YKTiNA IlAMII.I"M.r.^^ (Malll. 

 Cyrtia //">/'/' 1 1 alii. 'I'enth k'-| nrt on the Mate Cabinet, p. M'.''.. 



// i Hillin-j- ^ Series, 1 "i. \" |., p. jr.i 1 . r 



- -S2. 



M1.-.11). Pal.Mew York, Vol. IV.. p. L'I;S. l'lat<- \\VII.. figa 1-4, 



: \-.r>. .J,|\\. Figs. 26-33, and 38 .'iL'. 



-hell more or less triangular or sub-pyramida] , hinge-liae equal to the -reate-t width ..f 



the shell ; proportion- of length, breadtli, and h.-L-ht variable, 1-ut t're.|iieiitly the width i- 

 e 1( ual to the 1,-irjth nf the Neiiti'al valve, and the hei-ht of are ( i- ijiial In tin- lenjth of the 



dnr-al valve; .-iirf.ee plicate Ventral valve quadrilateral in outline, obliquely sub-pyramidal, 



iim-t prominent at the ln-ak, whieli i-\a-r\ \ariable in elevation and straight or :i little :in-ln-d 

 i- the area, and not iiiilreijiieiitly attenuate and di-t'-rted '-r turned t.. m, nie-ial 



-inu- wide and -tronidy delin'-d, I'Minded nr -ill. an-ular in tlie botinm ; area variable. 1. 

 and elevated, plan.- nr arcuate in different . with the hit. ral inaivin- an-ular. di- 



tinctly -triad- in l>ntli direct inn- ; li--mv n.ai : : i.\ a " . . \ pwudo-deltidium, w 1 1 it'll 



i- perforated abn\e by an n\al or narr.'ulv nvatc fur unen |l..r-al valve depressed, 

 with a broad, nmre or !-- pri.mim-nt nie-ial fnld, \\liieh i- b<Mind.-d b\ limader furr<>\v- 'l" : "i 



those betwi plications, and is sometimi d in front ; the!,. 



ri-m_' abnve the hiie_'e liiie . .in-a narr.av. iim-ar. but .jiiite di-tinet I \>\ al">ut 



-IX tO ej._'||t I! liu nr t'.Vn || Ullded plicatinll- n|| either -id'' nf the 111 



fnld and -inu-, and t lie.,- .ire . tine c,,ncent rie Unesof growth, which at inl 



li'c.ilue emwded and -lib imbiiea: ;al!\ Inward- tin- margins '!' "hler -lie)]-. Tlie titu'l 



-iirfaei- markinj i- minutely -r.anul- - Ot p-ipil',..-.-. and the -lidl -trueture i- di-tinetly 

 punctate In -..me of the laivr indi\ iduaN t h.-i i an olevatlOO on each 



the .-inu-. rt-embliiiL- an ,,},-,. let.- plie.M inn. 'I'lie Imijit udinal m. di in -.plum xt. ml- for 

 more than hall tl : , ..f I h.- \< nt ral valve, an. 1 i - emitinued int.. t !,, ,- r. ly I .em-atb" 



i-eiido di-lti'liiim. 'I'he-e feat ui. ..\MI iii :nl iii tran-\r-e -.etintis nf tin 



