127 



the ventral valve has a superficial resemblance. The ventral valve of A. umbonata is readily 

 recognized by its very gibbous form, its extremely elevated ;iud incurved beak, its possession 

 of a distinct mesial sinus extending from the beak to the front margin, and the existence of a 

 high and conspicuous area with a well marked h'ssure. 



Locality and Formation. Corniferous Limestone, Port Colborne. 



160. CRANIA CRENISTRIATA (Hall). 



Crania, crenistriatu (Hall), Thirteenth Report on the State Cabinet, p. 78. 



Crania cremstriaia (Hull), Pal. N. >'., Vol. IV, p. :>8, PI. Ill, fi-s. 1316. 



On examining the surface of some of the HcHijihijlhi of the Hamilton group, to which 

 so many small organisms are attached, I find several specimens of r/-<< (Hall). 



The dorsal valve of this species is all with which I am acquainted, uud it is depressed-conical, 

 nearly circular, with a central or sub-central apex. The apex i smooth, and the remainder 

 of the shell is covered by sharp elevated crenulate radiating striae, which increase interstitially, 

 and of which there are about ten in the space of one line at the margin. The diameter of 

 an individual of medium size is two lines and a half the height of the valve being little over 

 half a lino. 



The ventral valve has never been detected, and Hall has only seen four specimens of the 

 dorsal valve ; but the species does not appear to be very rare in the Hamilton shales at Arkona. 



Locality and Fonnatim. Hamilton Formation, Lartletts' Mills, near Arkuna, Town- 

 ship of Bosanquet. 



LIST OF FOSSILS FROM THE CORNIFEROUS AND II A 

 MILTON FORMATIONS OF WESTKKX ONTARIO. 



(The letters C. and 11. indicate the occurrence of the fossil in the Corniferoafl Lim* -t.'ii. 

 or Hamilton Formation.) 



I. PRnTOZi' \. 

 1. A-tnr.p-pnMiria Hani'ibmim-i-, Mttk (Uld Wortktn f i < ' 



L'. Btxomatopon taberoulata, A'/<7i/.<"/' <('). 



|..Ti;.rat:i. .\ , /<>/.< , C 

 I. -raiiillata, A hoi ' :'i>l 1 1 



5. inaiMMiillata, A ' i I ' 



6, " c..nr, ntrira. ',' Id) ' . 



II ' I:\TA. 



7. BlothrophyUam di'i-iirtiratiiin. /.' < 



a|i|irxiin itniii, A ' 



!'. < 'li-i'i|.liylluiu ( )n<-i'l.i. DM, / ' 



1". j.liirini.li.i . 



1 I. /.ipllivilti- .i-_':int.- I. / s ' 



1 '_'. II-M. ' 



13. |.r..liii.-:i. BiUn 



l i. /; C 



