626 Ry 
PLATE VL " ™. 
Figs. 1-4. Zarphyceras extensum, Quebec Group; Loc., Port au Choix, New- 
foundland. Reduced one-third. Fig, 1, lateral view, showing position of siphuncle, 
septa in section and free volution. Fig. 2, section of living chamber at the ter- 
mination restored by observation of the more perfect parts of the same volution. 
Dorsum appeared to have no impressed zone in this obviously the gerontic stage. 
Fig. 4, section of two ephebic whorls in part restored, showing impressed 
zone and general form. Fig. 3, section of younger whorl, restoration in part. 
‘Dimensions are incorrect in these sections, but the form is correct. 
Figs. 5-8. Aphetoceras Americanum, Quebec Group; Loc., Port au Choix, 
Newfoundland. Reduced one-third. Fig. 5, side view showing gyroceran mode 
of growth, suture with ventral lobe and younger sutures with ventral and dorsal 
saddles. Fig. 7, section of the outer whorl. Figs. 7, 8, sections taken at the 
two contiguous breaks in the outer and next inner whorls. Dimensions of these 
sections are not correct, but form is properly represented, 
Figs. 9-11. Litoceras tnsolens (?) (sp. Bill.), Hyatt, Quebec Group; Loc., 
Gargamelle Cove, Newfoundland. Fig. 9, side view of young specimens, very 
nearly natural size Fig. 10, interior whorls enlarged to show large umbilical 
perforation, costations of metanepionic, payanepionic and ananeanic substages, 
and the loose coiling of the ananeanic substage. Fig. 11, section of nepionic, 
ananeanic and anephebic volutions showing the absence of impressed zones in 
the nepionic and changes of form in older whorls. Compare this with the young 
of Trocholitoceras Walcottt. 
Figs. 12-20. Zrocholitoceras Walcott?, Quebec Group; Fort Cassin; U. S. 
Nat. Museum, Walcott Coll. Fig, 12, side view of type specimen natural 
size. Fig. 13, section of same. Fig. 14, section of centre of same enlarged to 
show the largest diameter of the umbilical perforation and the ananepionic sub- 
stage and paranepionic with impressed zone. Fig. 20 gives location of this section 
and all the rest are taken between the two bisecting lines of this figure. Figs. I5— 
Ig, successive sections gradually passing out of the umbilical perforation and 
showing the position of the siphuncle and increasing depth of the impressed zone 
after contact These sections also show that the impressed zone occurs after the ” 
gyroceran bend in the beginning of the paranepionic substage, and is apparently 
a result of the great increase in transverse diameters, nephritic form of whorl 
and abrupt befding. Fig. 20, location of sections, ideal. The shape of the ana- 
nepionic volution in Fig. 13 is more accurate than in Fig. 14 or 15. 
Figs. 21-27. Schroederoceras teres (sp. Eichw.), after Holm, P2/. 46h, Dames 
et Kayser, iii, Pl. vy. Figs. 21 and 22 show the subventral czecum in apical 
chamber and shifting of position to dorsad of centre in the ananeanic substage. 
Compare with Schroederoceras Latoni, Fig. 35. Figs. 23-27, ananepionic, 
metanepionic substages, the septa belong wholly to the metanepionic. There is 
no dorsal furrow in this shell until the third septum is reached and by comparing 
this with sections, Figs. 21 and 22, it is seen that this indicates e‘ther the begin- 
ning, Fig. 21, or the completion of the gyroceran bend, Fig. 22, although Holm’s 
Fig. 25 would lead to the supposition that the bending had not yet begun. 
Figs. 28-35. Schroederoceras Eatont, sp. Whitf., Hyatt, Quebec Group; Loc., 
