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the possession of very slight folds or nascent costations, which ap- 

 pear in some casts, as in the side view Fig. 17. 



These specimens occurred in a dolomitic limestone, on a hill to 

 the west of the inside beach of Port au Port, in the calciferous of 

 Murray and Howley. 



Tarphyceras prematurum, n. s. 



Loc, Port au Port, Newfoundland. 



PL iv, Figs. 12-16. 



This species is apt to be confounded with Tarphyceras Aucoini, 

 but the whorls increase faster by growth and are much larger at the 

 same age. 



Fig. 14 shows in part the nepionic whorl of this species and the 

 ananeanic substage. The section of the ananeanic whorl above the 

 ananepionic apex is restored, and is probably made too angular and 

 the abdomen too broad. The other parts of the figure are accurate. 

 The side view in Fig. 15 gives the same showing the prominence 

 of the early nepionic substages and the first of the paranepionic. 

 Fig. 16 shows the paranepionic and earlier substages from the 

 front. These figures give satisfactorily the differences between the 

 young of this species and Tarphyceras Aucoini. 



The presence of a very narrow umbilical perforation is plainly 

 evident in this specimen and this is similar to that of Aucoini, 

 The metanepionic dorsum is distinctly separated from the parane- 

 pionic dorsum, here shown in outline on the inner edge of the sep- 

 tum, by a narrow, smooth space which curves around between them, 

 but in consequence of its ventral curvature as it crossed between 

 them it cannot be seen in a side view. This perforation or bend is 

 larger and wider than in Aucoini, and the involution or ingrowth 

 of the nascent umbilical shoulders is less than in Aucoini. It is 

 consequently doubtful whether the abruptness of the curvature and 

 the ingrowth of the umbilical shoulders fully accounts for the pres- 

 ence of the dorsal furrow in the dorsum of this specimen. The 

 condition of the specimen is not wholly satisfactory, otherwise a 

 more definite opinion could probably be given. The inner or dor- 

 sal surface of the ananepionic and metanepionic substages has been 

 more or less eroded and it is not practicable to say, as in Aucoini, 

 that they might have influenced the formation of the outline of the 

 opposing dorsum of the paranepionic whorl as it was bent around 

 the umbilical perforation. 



The shell in its later stages, as shown in Figs. 12 and 13, resem- 



