The Geology of the Lower Leigh Valley. 65 



fossils derived from the Dog Rocks section, but upon experience 

 of similar strata in other localities. According to the Survey, 

 there is an outcrop of the so-called Middle Miocene (Eocene) 

 about two and a half miles farther up the river, but as no fossils 

 are mentioned, we did not consider that there was sufficient 

 encouragement to search for it. 



We have now reviewed the principal eocene sections on the 

 Leigh. The number of fossil species collected from them amount 

 to 447, which are tabulated as follows : — 



enumeration. 



The only recent species of MoUusca recognised are : — 



Hipponyx antiquatus Ostrea hyotis 



Crepidula unguiformis Axinjea laticostata 



Dentalium lacteum Limopsis belcheri 



Saxicava arctica ? 



and the proportion of living to extinct forms is therefore 1"7 per 

 cent. 



For Muddy Creek and Spring Creek, the distribution is fully 

 given in our list ; for other localities only occasionally. 



Fossils collected only from sections south of Shelford are 

 denoted by an asterisk, and from those to the north only by a 

 dagger ; in a few cases there is some uncertainty concerning 

 this special record, and a query is then prefixed When no sign 

 appears before the name of a fossil it is common to both the 

 north and south sections. 



For the identifications of many of the species listed we have 

 consulted Professor Tate, who most willingly placed his wide 

 knowledge of tertiary mollusca at our service. 



