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lar to those of Aphetoceras, but the whorls are in contact either in 

 the earlier epembryonic stages or throughout the ephebic stage. A 

 departure from the spiral regularly takes place in the gerontic stage 

 or earlier ; sometimes the entire ephebic stage is free. 



No impressed zone has been found at any stage, although a slight 

 flattening of the dorsum was observed in one species. 



This group is represented by several species in the Newfoundland 

 basin of the Quebec fauna, but it is only necessary here to describe 

 one. 



Deltoceras planum, n. s. 



Loc, Port au Choix, on north side, Newfoundland. 



This fossil is apparently very close to Barrandeoceras natator, 

 but it increases more rapidly in the dorso-ventral diameters and 

 has a larger siphuncle, and this is closer to the venter and it differs 

 also in the greater compression of the form. 



In the neanic stage it agrees more closely with natator in aspect, 

 but the siphuncle is subventran. In the ephebic stage and anage- 

 rontic substage it becomes propioventran and increases in size until 

 it becomes 7 mm. in diameter ventro-dorsally where it enters the 

 living chamber. The transverse diameter was not measurable, but 

 it is undoubtedly less than this in correlation with the compressed 

 character of the volution. The ventro-dorsal diameter of the last 

 whorl through the living chamber is 53 mm., the transverse 

 only about 28 mm. to 30 mm., the whole diameter of the coil 

 at this place being 163 mm. 



The incomplete living chamber is over one- quarter of a volution 

 and has departed slightly from the closer spiral of the ephebic stage. 

 This departure is very gradual at first until the gerontic stage begins, 

 and then becomes more apparent and widens more rapidly. The 

 whorls are in absolute contact only in the neanic stage. The venter 

 appears to be rounded at all stages of growth. 



Barrandeoceras. 



This genus was described in my Genera of Fossil Cephalopods to 

 include shells having large umbilical perforations, compressed 

 slightly costated or smooth whorls. The venter usually narrower 

 than the dorsum, the whorls barely in contact or with very slight 

 contact furrow, siphuncle near but above centre, septa deeply con- 



