BEEKMANTOWN AND CHAZY FORMATIONS OF CHAMPLAIN BASIN 473 



Position and localities. In the dove-colored Chazy limestones, 

 exposed two miles west of Little Monty bay near Chazy N. Y. ; on 

 Isle La Motte and on Yalcour island. In the first locality it has 

 been observed in several specimens b_y the writer but only in a poorly 

 preserved or fragmentary state of preservation. The second locality 

 has furnished the type specimen of the species [coll. by Professor 

 Perkins and now in the collection of Burlington University, Vt.] 

 and from the third a specimen has 

 been secured by Professor Hudson. 



Observations. This is the first 

 representative of the genus Tarphy- 

 ceras that becomes known from 

 rocks younger than the Beekman- 

 town formation. It is easily dis- 

 tinguished from all of its Beekman- 

 town congeners by its much shal- 

 lower cameras (or more closely 

 arranged septa), and also by its 

 greater rate of growth. In the lat- 

 ter character it approaches the 

 genus Eurystomites without how- 

 ever fully attaining the rapid 

 growth of the typical representa- 

 tives of that genus. It reminds also 

 of the latter genus in its great umbilical perforation and the posi- 

 tion of the siphuncle close to the ventral side. The latter position 

 of the siphuncle already in the- first volution, the close arrangement 

 of the septa, the early attainment of maturity and the beginning of 

 evolution at the third whorl give this species the aspect of a 

 phylogerontic form, when compared with the congeners from 

 the preceding formation. 



Fig 



Fis 



33 



Fig. 32 Tarphyceras multi- 

 cameratum sp. nov. Transverse 

 section of type, x?^ 

 Fig"- 33 Same. Section at beginning 

 of living chamber, x^^ 



Genus aphetoceras Hyatt 

 Aphetoceras farnsworthi (Billings (sp.) pars) Hyatt emend. 



Lituites farnsworthi Billings (pars). Pal. Foss. 1861. 1:21, 



fig. 24 

 Aphetoceras farnsworthi Hyatt. Am. Phil. Soc. Proc. 1893. 



32:448 



Of this species it is stated by Hyatt : 



This species probably belongs to a distinct genus, and is cited 

 here provisionally under this name because it may be merely a 

 highly degenerate species of Aphetoceras. It is also coiled in the 



