183 



conclusions previously arrived at. It seems needless to furnish a 

 list of the species, as I hope at an early date to examine exhaus- 

 tively and report upon the fauna as a whole. 



Below the chief shell-deposit, from 395 to 450 feet, species of 

 mollusca prove to be rare and in a fragmental condition. The 

 few forms which seem largely to make up the more calcareous 

 portions, included within the depths of 605 and 738 feet, afford 

 no very trustworthy index to age, of these Bitrypa W ormhetensis^ 

 McCoy, which is the most abundant, has hitherto been known to 

 me only from undoubted Eocene-beds, but as it is associated in 

 the higher levels of the Croydon-bore with some determinable 

 fragments of the characteristic mollusca of this formation, it must 

 be conceded that this dentaloid annelid is a survival from Eocene 

 times. 



The great thickness of the Older Pliocene, 406 feet at the 

 least, is unexpected, as I had conjectured that its base was near- 

 approached in the Dry Creek -bore at a level corresponding with 

 the superior beds only passed through in the Croydon-bore ; but 

 admitting the correctness of the assumption, then, the new facts 

 simply indicate a great inequality of the floor on which the Older 

 Pliocene deposits have accumulated. 



Section of the Strata passed through by the Croydon- 

 bore. 

 " mammaliferous drift." 



