156 CONTRIBUTIONS TO CANADIAN PAL^ONTOLOaT. 



diameter, aperture narrowly sagittate, its base deeply emarginate by 

 the encroachment of the preceding volution. 



Surface of the sides of the outer whorl marked by broad and rather 

 distant, radiating, bifurcating and doubly flexuous raised plications, 

 which commence at the umbilical margin, curve at first gently for- 

 ward, then as gently backward, and are finally bent very abruptly 

 forward next to the periphery, upon which they form narrow, elon- 

 gated and acute tongue-like processes. In addition to these plications 

 the surface is marked by tine, simple and comparatively close set, 

 radiating, raised lines, which are also doubly flexuous on each side. 

 These raised lines are most strongly marked on the outer half of the 

 sides, and are as well defined on the summits of the plications as in 

 the smaller spaces between them. Septation unknown. 



K-uk Eiver, coast of British Colambia, G. M. Dawson, 1885: one 

 tolerably well preserved but somewhat imperfect cast of the interior 

 of the shell, whose greatest diameter is a little less than five inches. 



This species seems to be most nearly related to the Am^nonites 

 hicuroatus of Michelin, from the Gault of France, as figured by 

 d'Orbigny on Plate C4, figs. 3 and 4 (but not figs. 1 and 2 of the same 

 plate, which, accoi'ding to Pictet, represent A. Clean, d'Orb.) of the 

 Atlas to the first volume of tjie Pal^ontologie Prangaise, Terrains 

 Cr^tac(5s. It seems, however, to differ from A. blcurvatus, which Zittel 

 places in Meek's genus Placenticeras, notonljr in its much greater size, 

 but also in the presence of numerous, closely arranged and doubly flex- 

 uous raised lines, in addition to the doubly flexuous radiating plications 

 or rib-like folds which are common to both. 



Placenticeras Perezianum. 



Ammonites Perczianus, Whiteaves- 187G. Geol. Surv. Can., Mesoz. Foss., vol. I., 



p. 19, pi. II„ iigs. 1 and 1 a- 

 HaplocerasPerezianum,Wh\tea,vea. 1884. lb., p. 204. 



Liard Eiver, below Old Fort Halkett, in latitude 59° 2(5' an d longi- 

 tude 124° 48' W., R. G. McOonnell, 1887: two specimens, which though 

 a little larger, seem to be precisely similar in all other respects to the 

 type of A. Perezianiis from the Queen Charlotte Islands. In one of the 

 specimens from the Liard Eiver nearly the whole of the sutural Hue is 

 well preserved, but the exact shape of the siphonal saddle cannot be 

 ascertained, though it was evidently very small. The first, second, 

 third and fourth lateral saddles, which diminish gradually in size 

 towards the umbilicus, are variously but unequally branched and 

 incised, and are succeeded in the umbilical I'egion by four or five 

 small unbranched saddles with incised margins. The siphonal lobe is 

 moderately large and is divided at the summit into two equal parts by 



