AMI ornEK WORK IN nKRTS. 113 



" The most striking and interesting feature of the Chalk Rock is 

 its palaeontology ; in the first place, fossils arc very much more 

 abundant in it than in the overlying and underlying beds, and, 

 secondly, the general facies of the fauna is jieculiar, owing to the 

 presence of genera and species not found in the other zones of the' 

 Upper and Middle Chalk, and also to the abundance of certain 

 groups, especially the cephalopoda and gasteropoda, which are com- 

 paratively rare in the beds just above and below. As a whole the 

 fauna presents a much greater resemblance to that of the Lower 

 Cenomanian [Lower Chalk, or Chalk MarlJ than to any which 

 occur in the divisions of the Senonian [Upper Chalk] and Turonian 

 [Middle Chalk] above and below it ; and whereas the latter are of 

 a deep-water type, that found in the Chalk Rock is certainly of 

 a comparatively shallow- water character." 



"When Mr. \Yoods says that in my first description of the Chalk 

 Rock I "regarded "it as occurring between the Upper and Lower 

 Chalk," instead of between the Upper and Middle Chalk, he 

 apparently forgets that at the time Middle Chalk had not been 

 invented, that division then being merged with the Lower Chalk. 



He suggests that, on account of its marked palEeontologic 

 characters, the Chalk Rock should have a zonal name, and is 

 inclined to propose that of the "zone of Heteroceras Reussianum,^^ 

 or '^ Heussianum-zone.'^ For my own part, I much prefer the 

 simple English term, not because I was godfather, but because 

 I like plain English, and also because, judging from what is 

 constantly happening, palasontologists will in all likelihood some 

 day change the name of Heteroceras Reussianum into something 

 totally different. 



In the first part of the paper the Cephalopods and the Gasteropods 

 are descrilied in detail, and a table of the range of the species, both 

 in England and abroad, is given, Hitchin figuring as one of seven 

 localities from which fossils have been recorded in quantity. 



The second part deals with the Bivalves in like detail, but 

 Hertfordshire does not find a place in the five English localities 

 noted in the table. The "Distribution and Relations of the 

 Pauna " are then treated of, but this lies to a great extent far 

 beyond our border. A list of the species of Mollusca confined to 

 the Chalk Rock in England is given; the most noteworthy points in 

 the Mollusca are noticed, such as the rarity of Astreidoe, Pectinida), 

 and Limna^idse amongst Bivalves, and the absence of Crustacea 

 (except PoUicipes) ; and a list of the fossils other than the 

 Mollusca is added. The "Conditions under which the Chalk Rock 

 was Deposited " are then considered at some length, the conclusion 



