309 



" The specimen is imperfect ; but if it has not been compressed laterally, 

 then, as nearly as I can determine, the dorso-ventral diameter at the end 

 of the fifth -whorl is sixteen lines and the lateral twelve ; at the fourth 

 whorl five to seven ; and it would appear therefore that the third must 

 be scarcely three lines in its greatest diameter. 



" I have not seen the first and second whorls, but as there is an empty 

 space nine lines in diameter in .the centre of the coil, I presume that they 

 did once exist and occupy that space. The whorls are in contact, but the 

 outer ones are not indented by those next preceding. 



" Locality and Formation. — Mingan Islands ; Chazy limestone. 



" Collectors.- -^it W. E. Logan, J. Richardson." 



The original label is not preserved and the exact locality from which the 

 specimen was collected is unknown. The label now attached to the 

 tablet upon which it is placed states that it was collected in 1856. 



The same specimen is thus described by Hyatt, under the name 

 Barrandeoceras natator, in his " Phylogeny of an Acquired Characteristic." 



" This species has volutions compressed oval in section, the dorsum 

 somewhat broader than the venter ; siphuncle is extracentroventran, even 

 in the neanic stage ; septa deeply concave ; sutures with dorsal and ventral 

 saddles and the lateral lobes as in other species of the genus. 



" The volutions are in contact, but no contact furrow was formed at 

 any age. The contact takes place as in the young of Estonioceras per^ 

 foratum, on the venter of the paranepionic volution. 



" The volution in the neanic stage, dorso-ventral diameter 13 mm., has 

 a much narrower venter in proportion to the dorsum than in the adult. 

 The venter was rounded at all stages and also the dorsum. The aneanic 

 and nepionic stage were not present in the original specimen in the Museum 

 at Ottawa, but in following out the same lines it is easily ascertained that 

 the umbilical perforation must have been enormous, at least 15-17 mm. 

 in diameter. The living chamber was somewhat over one-fourth of a 

 volution in length. The whole diameter was about 108 mm. It was 

 reported as having been found in the Chazy limestone." 



(2.) Barrandeoceras Minganense, Hyatt. 



Barrandeoceras Minganense, B.y3.tt 1894. Proo. Amer. Phil. Soo., vol. 



XXXII, p. 451. 



" Loc, Mingan Islands. 



" There is a specimen from the Chazy limestone of the Mingan Islands in 

 the collection of the Museum of the Geological Survey at Ottawa which 

 has very similar characters to those of Barrandeoceras natator, but is 

 distinct in some of its characters. The living chamber is short and, if 

 complete, about a quarter of a volution in length. It is free and in section 



