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and the lines are almost straight on the sides. The lines of growth 

 alone are visible. There are no prominent bands marking perma- 

 nent apertures, nor are the characteristic costae of Trocholites 

 visible, nor any longitudinal ridges in my specimens. Growth 

 lines show that in the nepionic stage not only the form and sutures 

 were distinct but also the aperture. The apertures are trumpet- 

 like in the ephebic stage and have a moderate hyponomic sinus 

 with broad lateral crests, increasing in prominence towards the 

 dorsum. Whether there are sinuses in the contact furrow has not 

 been determined, but one infers their presence because the lines of 

 growth incline apically just before reaching the lines of involution. 

 The form of the whorl continues rounded in all species of this 

 genus, although in some there is a distinct tendency towards angu- 

 lation of the sides. 



The contact furrow appears very early in consequence of the 

 close coiling of the whorl. This zone is not deep, but it is well 

 marked and may extend nearly to the abdominal angles in some 

 species and it remains throughout life. So far as known no specimen 

 has been found with even a part of the last whorl free. The form 

 of the whorl in section is consequently nephritic, except in some 

 species having flatter sides and more pronounced abdominal angles 

 than usual. 



In one species only, T. circularis, is there any tendency to form a 

 pentagonal whorl and this was not only very obscure but observed 

 only in one specimen, the type form. The whorl is therefore very 

 primitive. 



The length of the living chamber is given as usually about three- 

 quarters of a volution by Schroder, but some of his species have it 

 less than one-half of a volution. T. Remeki and T. ammonius\\d,\^ 

 one invariably somewhat less than one half of a volution in length. 

 It is obvious that in this genus it varies between these limits. 



Trocholites internastriata. 



Lituites internastriata Whitf. Fort Cassin Foss. {Bull. Am. 

 Mi/s., New York, i, No. 8, PI. xxix, Figs. 5-8). Fort Cassin. 

 This species, of which I have studied the originals, has young of 

 cyrtoceran form, with a good-sized umbilical perforation, as in 

 Schroederoceras and Litoceras. The siphuncle is centren in 

 what is probably the second septum, and it has not the prolonga- 

 tion beyond this septum, as figured by Whitfield. It inclines 



