437 
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, D. S. 
Loc., Port au Port, Newfoundland. 
Pl, iv, Figs. 12-16. 
This species is apt to be confounded with Zarphyceras 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 Zarphyceras Aucoin. 
The presence of a very narrow umbilical perforation is plainly 
evident in this specimen and this is similar to that of Aucoznz. 
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 Azcoznz, and the involution or ingrowth 
of the nascent umbilical shoulders is less than in Auco‘nt. 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 Azucotnt, 
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- 
