564 Annals of the Carnegie Museum. 



S/rophoniena prisca, Scenella pretensa, Scene/lam otitrea/oisis, Palceac- 

 nuea irregu/a/i's, Raphistoma iinmaturum, and Scalites angulatiis. 



Others which occur in this zone abundantly are : Blastoidocrinus 

 carcharicedens, Bolboporites americanns, Zygospira aciitirostris, Raphis- 

 toma staviiueum, Lophospira suhabbreviata, Bucania sulcatina, and 

 PseiidosphcErexochus chazyensis. 



Those which occur only rarely in this division, but which have not 

 so far been found in the higher divisions, are Lingiila belli, Cyrtodonta 

 soli/aria, Kiinenia Icpto'iotuni, and IPcliomcra sol. 



Of the 141 species in the Chazy whose range is known, 64 make 

 their first appearance in this horizon and 23 of these are found in all 

 three divisions. 



The division is characterized by the predominence of individuals 

 and species of brachiopods, 14 of the 25 brachiopods, which occur in 

 the Champlain Valley, being found in this division, while only 2 of 

 the 16 pelecypods are represented. Exactly half the species of trilo- 

 bites are found in this lower division, but individuals are not common. 

 There are more of the gastropods, half the species being represented, 

 and individuals of some of these species are very numerous. The 

 gastropods do not occur in the lower part of the strata of this division, 

 but are confined almost entirely to the upper part. 



This division is further marked by the api)earance of the earliest 

 of American Bryozoa.^'' Unlike most Ordovicician species, these range 

 throughout the entire formation, above the basal sandstone. 



There are three zones in this division which are worthy of notice. 



Zone I a. Tlic Orthis atiitiplicata zone. 



This zone is near the base of the division and is found at \'alcour 

 Island and Isle La Motte. The characteristic fossils are : Ortliis aciiti- 

 plicata, Rafiiiesquiiia iiicrassala, Isotcliis harrisi, and Thaleops ovata, 

 all species with long ranges except the first. 



Zone lb. The Scalites aiigi/lati/s zone. 



The faunule of this zone is found at Plattsburgh and Chazy. It is 

 located at the middle of the division. Characteristic fossils are: Sca- 

 lites angiilatus, Raphistoma immati/nim, Bucania sulcatina, Raphistoma 

 staminci/m, Canierella longirostris, lllceni/sglobosiis, and Thaleops ovata. 

 Only the first two are restricted to this horizon. 



Zone ic. The Lophospira suhabbreviata zone. 



36 According to Nickles and Bassler, Rhinopora prima Whitfield, from the Beek- 

 niantown, is probably not a Bryozoan. 



