Clarke — Early Stages of Certain Goxiatites. 



169 



distal extremity, these lines continuing without noticeable increase of size for 

 a half revolution of the conch. In later growth these striae develop into more 

 distant, elevated, sinuous lines, eventually, in adolescent stages, becoming dis- 

 tant, low l ibs. At maturity such ribs are obsolete or may rarely manifest them- 

 selves as a row of nodes near the umbilical margin. There is complete contact 

 between the protoconch and the nepionic whorl. We have noticed above the 

 character of the Axarcestes protoconch described by Holzapfel; a form 

 similar in all respects to that of Agon, eoepansus (size not included, as the 

 author has given no dimensions for his specimen), save that in the former 

 the protoconch is free from the first half volution. No evidence of any such 

 mimoceran phase has been seen in any of the goniatites examined by me. A 

 portion of the shell of the specimen here figured is so broken as to expose 

 the long and strong impression of the siphonal caecum. This specimen is from 

 the Agoniatites limestone at Manlius, X. Y. 



The protoconch of this genus has already been represented by Branco 

 in the species, Gon. evescus, von Buch. (See Palaeontographica, vol. xxvi, 

 pi. vii, figs. II, a-e, 1881). This has a relatively greater Avidth and is hence 

 more ellipsoidal than in Gon. expansus. It is, moreover, of notably less size 

 than that of the latter. That of Goniatites evexus has a width of 1 mm., 

 while this dimension in Gon. expa.nsus is 1 . 7 mm. The figures by Braxco 

 show no surface ornament on the protoconch. 



Nautilus (Eutrepkoceras) DeEayi, Morton. Fox Hills Group, Montana. This is a ver- 

 tical section through the fir>tt three air-chambers and shows the irregular curve of the siplio 

 which Ins either been almost entirely calcified or rilled with a deeply discolored calcite and 

 presents an unbroken course. 



