418 Notices of Me mot rs — Popcrs read <it lirifis/i A-^.socinfioii. 



This fossil therefore cannot be oallod either Avicula filata or 

 Ostrt'd rci^lciiloixt. for in the former the <j;eneric name is incorrect, 

 and ill the hitter tlie specific name already belono-s to an entirely 

 diiTerent species from Warminster. The obvious course is to call 

 it Ostvca filata. 



IV. Tub ' Lowku IIolastku Zonk.' 

 A brief comparison of the values of the two ITolasters for zonal 

 })iirposos may be made as follows : — 

 llolatitcr fiulxjlohosus. 



(1) l^oos not often reach the top of its zone. 



(2) In the type locality it only reaches half way. 



(3) Is sometimes entirel}' absoiit from the zone. 



(4) Is general I3' abundant in the zone below. 

 Jlolasler trcceusix. 



(1) Occurs up to the summit of the zone. 



(2) Is rarely absent, but in Cambridgeshire does not occur in 



the lower half of the zone of 11. stihglohonns. 

 (8) Is ver}' rarely found associated with A. vnrtnns. 



Thus neither of these fossils is really fitted for zonal use, and of 

 the two, //. stihglohosnn is the least suitable. But a fairly satisfactory 

 zone might be defined as the ' Lower llolaster Zone ' by using the 

 two Ilolftsters in partnership ; for one or other of them is nearly 

 always present in every part of the Chalk which occurs between the 

 zone of A. v<trians and J>. plena throughout liritain. 



The following anangemeut of the Chalk of Cambridgeshire is 

 therefore recommended : — 



Micraster zones ( Upper Chalk and Chalk Rock nm\ 



JlolaxtiT plaints 7,ono ... ) Holaster pltinm hcAs. 



TorhratnUna lata zone ... \ 



M. Ciivieri zone f MuWIo Chnlk, TSIelhouru Rock, 



' jHOcnamtis labiatiis ?.ono ... l ami Bolemuite Miu'ls. 



Ji. pliNU zone 



Two Ilohistors Zone 



A. vanaiis zone 



) Chalk with Jf. tircrnitiii. 

 \ Chalk with II. suh^/lul>osits. 



I Buvwoll U(»ok. 

 \ Chalk atari. 



3:<roTiCES o:f IsKJei^oxtis, eto 



I. — BuiTlSn ASSOOI.XTION for TUK Am ANOlCMKNT OF SOIKNCR. 



SBVKNTY-Sixrii Annual Genkiial IMKK'riNa, hklp at Yokk, 

 August 1st to 8th. 1906. 



Tresident: Trofossor E. Ray L.\nkestf.k, ISf.A., LI-.D., D.Sc, F.R.S., F.L.S., 

 Director of the Natural History Departments of the British Museum. 



liiST OF Papkus Ekad in Skction C, Geology. 



Address by the President (G. W. Lamplugh, F.K.S.). 

 Frofessor P. V. Kendall — On the Geology of the Country round 

 York. 



