261 



rounded, closely coiled and increasing rapidly in size ; outer whorl inflated 

 and expanded, with two faint low rounded spiral plications near and at 

 the aperture in young specimens, and from three to four in adult ones. 



" Surface marked with numerous, close-set, transverse lines of growth, 

 that are flexuous where they cross the spiral plications. 



"Portage road at falls: oneapparently adult and one half grown specimen- 

 The former, which is well preserved and nearly perfect, is thirty five 

 millimetres wide, and was probably about thirty mm. high when perfect, 

 allowing two mm. for a small piece broken off at the apex. 



DiAPHOROSTOMA. PEEFOEATUM, Whiteaves. 



Plate 29, figs. 7, & la. 



Diapkorostoma 23erforatum, 'Whitea.vea 1904. Geol. Surv. Canada, Ann. Rep., vol. 



XIV, pt. F, p. 52. 



" Shell depressed turbinate, much wider than high ; spire short, raised 

 very little above the highest level of the outer whorl ; base narrowly but 

 deeply umbilicated. Whorls five, increasing rapidly in size, those of the 

 spire flattened above and rounded below ; the outer one rounded and 

 ventricose, but depressed at the suture above ; umbilical margin rounded 

 and very indistinctly defined. Aperture rounded subovate, pointed above 

 and slightly insinuated on the oolumellar side by the encroachment of the 

 preceding whorl, wider and rounded below ; lip thin and simple ; 

 characters of the columella not well shown in the only specimen collected. 



" Surface marked with numerous close-set, nearly straight and very 

 minute transverse raised lines, that are scarcely visible without the aid 

 of a lens ; also by a few larger and more distant impressed lines of 

 growth. 



" Middle rapid : one nearly perfect specimen, with the test preserved. 



"This shell seems to be referable to the genus Platyostoma, Conrad (1842), 

 but Lindstrom asserts that this name is preoccupied by Klein in 1753, by 

 Meigen in 1803, and by L. Agassiz in 1829, For this reason Dr. Paul 

 Fischer (in 1885) proposed to distinguish Conrad's genus by the name 

 Diaphorostoma, though Lindstrom maintains that both Platyostoma, Con- 

 rad, and Strophostylus, Hall, are mere synonyms of Platyceras. Fischer 

 explicitly states that the only difference between Diaphorostoma and 

 Strophostylus is the obliquely folded columella of the latter, while East- 

 man, in the first volume of his translation of Zittel's " Text-book of 

 Paleontology," quotes Strophostylus, Hall, as as synonym of Platyostoma, 

 Conrad." 



