BEEKMANTOWN AND CHAZY FORMATIONS OF CHAM PLAIN 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 Valcour island. In the first locality it has 

 been observed in several specimens by the writer bnt 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. 33 



Fig. 32 Tarphyceras multi- 

 cam e r a t u m sp. nov. Transverse 

 section of type. x% 

 Fig. 33 Same. Section at beginning 

 of living chamber. x T % 



Genus aphetoceras Hyatt 

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



Lituites farnsworthi Billings (pars). Pal. Foss. 1861. 1 :2I, 

 fig. 24 



Aphetoceras farnsworthi Hyatt. Am. Phil. Soc. Proc. 1803. 

 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 



