BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMTLAIN BASIN 447 



These are increased by interplantation and are, with the exception of 

 a few intercalated smaller ones, all sharply elevated and of uniform 

 size. There are about six of them 

 in the space of 3 mm. They are 

 continuous over the edges of the 

 annulations as stated by Billings. 

 In very well preserved specimens 

 there are about 10 in the space of 

 one line as noted by Billings but 

 these are so fine that they are 

 hardly noticeable to the naked eye 

 while lines about 1 mm distant 

 from each other are so prominent 

 that they alone appear to consti- 

 tute the longitudinal sculpture of 

 the conch. It is quite apparent that 

 the characters of the longitudinal 

 lines are variable in different 

 growth stages of the conch. The 

 annulations are rounded in our 

 specimens as they were described 

 by Billings though they often ap- 

 pear acute in natural sections on 

 account of the obliquity of the lat- 

 ter. In old age they become rela- 

 tively low and indistinct. The 

 interspace is always uniformly con- 

 cave. The annulations and septa 

 correspond in arrangement. 



The cameras are shallow ; where 

 the conch is 15 mm wide there are 

 counted y/ 2 of them in the space of 

 10 mm ; where the conch has grown 

 to a diameter of 55 mm the cam- 

 eras are 8 mm deep. The septa are 

 shallow, at the former place their 

 depth is half that of the cameras, 

 at the latter place it is equal to that 

 of ij/2 cameras. 



form observed, it is associated with small longitudinally striated conchs 

 [see pi. 16, fig. 7], which in the other specific characters fully agree with this 

 species, appears to us as fair evidence of the nonannulatcd character of the 

 earliest stages of the conch. 



Spyroceras clintoni Mil- 

 ler (sp.)' Natural section, x \ 



