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have ventral and dorsal saddles until the contact furrow is formed, 

 and then probably a ventral lobe is always generated. 



Barrande's figure of this species, PI. xlv, Fig. 21, gives similar 

 observations upon a different specimen. When the median ventral 

 zone appears, the broad ventral saddle becomes narrowed to the 

 width of this zone and the lateral lobes are proportionately broad- 

 ened out. 



Ophidioceras tener. 



Ophidioceras tener, Barrande (Sysf. SiL, PI. xlv); PI. viii, Figs. 

 24 and 25. 

 Loc, Bohemia. 



The specimen of this species, Figs. 24 and 25, gives the peculiar 

 and very large ananepionic substage of this species, and in the side 

 view the two marked constrictions indicating the same changes of 

 form as are described in Ophidioceras rude us, but subsequently 

 there is a marked bulging of the sides, in what has been termed in 

 other forms the metanepionic substage, beyond the second constric- 

 tion. If the first septum occurs where it is figured, the metane- 

 pionic substage must be placed in the Ophidioceran forms later 

 than in other forms like Nautilus pompilius, which have the first sep- 

 tum nearer to the apex, and the ananepionic substage must be con- 

 sidered as greatly prolonged. Although the specimen had a perfect 

 surface on the side depicted of the nepionic stage, it is possible 

 that there may have been other septa* between this and the apex, 

 but of so fragile a nature that they were not preserved. The 

 surface of this cast is iron pyrite. There are also six septa occupy- 

 ing the nepionic stage of this specimen. 



There was a minute circular mark on the apex, indicating the 

 position of the caecum to be propioventran, but this was not abso- 

 lutely certain. In the second septum the siphuncle was extracen- 

 troventran and in the neanic stage it attained a centroventran 

 position. The subsequent stages observed were similar to those of 

 Ophidioceras rudens except that the peculiar flattened ventral zone 

 of this species was introduced later than in that species, as described 

 and figured by Barrande. 



The primitive rounded outline of the impressed zone was main- 

 tained longer in this species than in Ophidioceras rudens. 



*SeeOphid. tessellatum. 



