283 



In the third part of this volume three imperfect and badly preserved 

 Ammonites from Cumshewa Inlet were identified with the Ammonites 

 planulatus of Sowerby, Sharpe and Stoliczka. The small one figured on 

 Plate 28, has part of the test preserved, but so much of the periphery of 

 the outer volution is worn away that its umbilicus appears to be wider 

 proportionately than it really was. In this specimen both the venter and 

 the sides are compressed, the transverse section being subquadrangular in 

 outline, but higher or longer than broad, and concavely emarginate below. 

 On the outer volution there are seven distant, slightly flexuous, transverse 

 constrictions, which are flatly arched in crossing the venter. The ribs, 

 which run parallel to them, are thin, sharp and separated by compar- 

 atively wide shallow grooves. The two large specimens referred to on page 

 207 are septate throughout and show the general shape fairly well, also 

 the characters and relative proportions of the umbilicus. In the larger 

 of the two the umbilicus appears to occupy a little more, and in the 

 smaller a little less, than one-fourth of the entire diameter. The larger 

 has all the surface markings obliterated by weathering, but the smaller is 

 regularly ribbed and marked by seven or eight distant constrictions on 

 the outer volution. The ribs are not very prominent, and narrower than 

 the grooves between them. 



Quite recently three specimens, which are apparently referable to this 

 variety of D. planulatum, have been lent to the writer l)y Dr. Newcombe. 

 One of these was collected at Cumshewa Inlet by Mr. Maynard Smith 

 in 1892, and the other two at Maple Island by Dr. Newcombe in 1895. 

 The Cumshewa specimen is a slightly distorted cast of the interior of 

 most of the septate portion of the shell, with small portions of the test 

 preserved. It measures about eleven inches in its maximum diameter, 

 and about four inches in thickness. It is much more convex proportio- 

 nately than the two large specimens from the same locality collected by 

 Dr. Dawson. Owing to the distortion, the comparative size of the 

 umbilicus of the specimen collected by Mr. Smith cannot be ascertained 

 with much accuracy, but it can scarcely have occupied much more than 

 one-fourth of the entire diameter. There are only five, distant and nearly 

 straight, transverse constrictions, on its outer volution. The ribs, which 

 though well marked, are low, rounded at their summits and narrower than 

 the grooves between them, are usually simple, with an occasional shorter 

 rib intercalated between two of the longer ones. The two specimens from 

 Maple Island are both much compressed laterally. The more perfect of 

 the two, the one figured, is a slightly crushed, septate cast about six 

 inches and a half in its maximum diameter, and about one inch and three- 

 quarters in thickness, allowing for the distortion. Its umbilicus occupies 

 nearly one-third of the entire diameter, and on its outer volution there 



