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Mr. Stanton has kindly examined the numerous specimens in the 

 National Museum, and estimates that the retroversal chamber in 

 this variety is generally the sixth or seventh volution and also 

 remarks that one specimen is nearly double the size of the largest 

 one mentioned above, and that there are but few that are smaller. 

 The three specimens I have of this variety are dextral, but there are 

 others in the National Museum which are sinistral. 



Var. prematurum. 



This variety has more closely set costae and smaller tubercles and 

 the gerontic stage begins earlier, there being, if my estimate is 

 correct, only three or four closely coiled whorls. The last volution 

 is well preserved in the only specimen of this variety that I have 

 and this shows clearly an open aperture, almost straight across the 

 venter, with slight crests on the sides and equally obscure crest on 

 the dorsum. It is, in other words, precisely similar to the aperture 

 of variety retrorsum. The specimen here described is sinistral, and 

 is the only one obviously belonging to this variety in the collection 

 of the National Museum. 



Var. aberrans. 



This variety may have three, four or five closely coiled whorls 

 and considerable variation in the tuberculations, etc., but when the 

 gerontic stage begins, the aspect is distinct. The anagerontic 

 substage does not bend so abruptly as in retrorsum or prematurum 

 it is more oblique to the axis of the spire and the retroversal meta- 

 gerontic substage, if it be superadded in this variety, would be more 

 oblique than in var. prematurum. One specimen is dextral and the 

 other is sinistral. 



Remarks. 



This species was discovered by Mr. Stanton in the Ripley beds, 

 where it is associated, as stated by the same gentleman, with a 

 number of other phylogerontic species, such as two species of 

 Ptychoceras, Turrilites splendens, Shum., Nostoceras (Turr.) heli- 

 cinum, Shum., Helicoceras navarroensis, Shum., and a variety of 

 other typical Ripley species. Mr. Stanton also informs me that out 

 of 26 specimens in the National Museum, 16 are dextral and 10 are 

 sinistral. 



