248 



mm. : height of aperture, nineteen m.m. : maximum width of the same, 

 ten mm. 



South side of Maud Island, seven small specimens, the largest of 

 which is not more than twenty millimetres (or a little more than three 

 quarters of an inch) in its greatest diameter. East side of South Bay, 

 in Skidegate Inlet (" probably from Subdivision E." Dr. Gr. M. Dawson) 

 two specimens, one of which is the largest tolerably perfect one that 

 has yet been obtained. 



At the last mentioned locality a large fragment of one of the whorls 

 of this species was collected which shows that the specimen when entire 

 must have been fully four inches in its greatest diameter. The ribs on 

 this fragment are fully five mm. apart, and there are no crenations on 

 its keel. At the South end of Maud Island, associated with the more 

 normal form, there occurs a variety which has a proportionately 

 narrower umbilicus, with somewhat steeper sides, but this variety 

 does not seem to be constant in its characters but to merge gradually 

 into the more typical form. 



Young specimens of the present species and of the Ammonites cordi- 

 formis of Meek and Hayden,* of about three quarters of an inch in diame- 

 ter, or a little more, are exceedingly alike, but at a slightly advanced 

 stage of growth, the former does not increase much in thickness, and 

 its keel becomes simple and entire, whereas the latter increases very 

 rapidly in thickness as it grows older, and its keel is always serrated. 



It is not without precedent for a species of Schloenbachia to have a 

 crenate keel in its young state and a simple keel when older, for 

 Stoliczka says that this is the case with his Ammonites Blandfordianusrf 

 which Neumayr places in the genus Schloenbachia. 



SPHENODISCUS EEQUIENIANUS ? d'Orbigny. 

 Plate 22, figs. 4 and 4o. 



Ammonites Requienianus, d'Orbigny. 1840. Pale'ontologiS Franpaise, Terrains 



Cretac6s, VoL 1, p. 315. pi. 93. 



South side of Maud Island : a badly preserved cast, which agrees 

 very well, on the whole, with d'Orbigny's description and figures of the 

 above named species, but as the septation is not visible in the specimen 

 collected by Dr. Dawson and as its outer edge is so much water-worn 

 as to obscure the true characters of the periphery, its identity with 

 A. Requienianus is rather suggested as possible than decidedly affirmed. 



See Plate 5 of the " Palaeontology of the Upper Missouri," figs. 2d and 2e. 

 t Palseontologia Indica. Cretaceous Fossils of S. India, Vol. 3, p. 46. 



