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The sutures have ventral and dorsal lobes and lateral lobes in the 

 ephebic stage, but in the earlier stage there are ventral saddles. 



Nephriticeras liratum. 



Nautilus liratus, sp. Hall {Pal. N Y, v. Pt. ii, PI. lvii and PI. 



lx). . 



This species in the metanepionic substage is distinctly annulated 

 and also has broad longitudinal ridges, as shown in Hall's figures 

 on PI. lx. These ridges disappear together with the annulations on 

 the abdomen of the paranepionic volution, but persist longer on the 

 dorsum, and in some specimens they are very large flutes On the 

 sides even in the neanic, as is shown in Hall's Fig. 3, PL lvii. 



In the neanic stage the form of the volution changes from sub- 

 trigonal to a broad depressed oval. 



No impressed zone has been observed, but this maybe due to the 

 age of the shells so far observed, none of which as figured, nor so far 

 as I have seen, exceeded one volution. 



Nephriticeras juvenis. 



Nautilus liratus, var. juvenis, Hall {Pal. N Y, v, Pt. ii, PI. lvi, 

 Figs. 5, 6). 



This shell, described as a variety of liratus by Hall, is obviously 

 distinct. The form changes more rapidly than in liratus and, in 

 the fragment of the nepionic volution figured by Hall, it may also 

 be seen that the longitudinal ridges are much smaller than in lira- 

 tus, more like those of the young of Nephriticeras bucinnm. It dif- 

 fers from the last in having no impressed zone at the same age. 



It is highly probable than an impressed zone appeared in a later 

 stage than has yet been described. 



Nephriticeras subliratum. 



Nautilus subliratum, sp. Hall {Pal. N Y, v, Pt. ii, PI. lvii). 



This species has similar changes of form to those of liratum, but 

 it is altogether a broader whorled species and acquires the nephritic 

 outline at an earlier stage of growth, and probably has in perfect 

 specimens a smaller umbilical perforation. 



There are no longitudinal ridges on the ventral side in the orig- 

 inal specimen, which was in the neanic stage of development, but 

 these are large and persistent on the dorsum as in Nephriticeras 

 liratum. In Hall's figures the sutures have been confused with the 



