' 163 



The following is the original description of " Lithostrotion Stokesi" : 

 ■" Polypierites cylindriques, parallMes, assez espac^s, presentant de forts 

 bourrelets d'ou partent des expansions murales unissant entre eux les 

 individus. Ces expansions ne sont pas tou jours completes, mais elles 

 ne paraissent jamais affecter la forme de tubes de connexion. Les 

 planchers 'sont bien developpes. Nous avons pu compter 36 cloisons tres- 

 minces, qui nous ont semble peu inegales et peu d^veloppees. Le diametre 

 des polypierites est de 5 ou 6 millimetres. Carbonifere. Amerique du 

 Nord: Lac Wennipepr. Coll. Stokes." This species was probably referred 

 to Lithostrotion, by Edwards it Haime, rather than to Diphyphyllum, 

 because the rocks from which it was collected were then supposed to be 

 of Lower Carboniferous age. In the description quoted, it will be 

 observed that there is no mention of any styliform columella, like that of 

 Lithostrotion, in the centre of the corallites, and there is no indication of 

 any such structure in the original jigure of L. Stokesi. 



A few well preserved, specimens, which agree very well with the 

 description and figure of L. Stokesi, also with Hall's illustrations and 

 vague diagnosis of his " Sarcinula (?) ohsoleta," but which are clearly 

 referable to the genus Diphyphyllum, as now understood, were collected 

 at Lower Fort Garry by Donald Gunn in 1858, and by T. C. Weston in 

 1884. These specimens consist of large portions of colonies of fascicu- 

 lated corallites, with few connecting processes between them. The coral- 

 lites average from six to eight millimetres in diameter, and are covered 

 externally by a thin, transvei-sely striated epitheca. When the epitheoa 

 is worn off or broken away, as it often is, the surface of the corallites 

 underneath it is marked with fine linear longitudinal grooves, corre- 

 sponding to the septa within. The internal structure of the corallites 

 consists of twenty-two long septa, alternating with as many shorter ones, 

 and of the usual transverse tabulse characteristic of Diphyphyllum. 



Streptelasma robustum, Whiteaves. 

 Plate 18, figs. 1 and la. 



Streptelasma corniruluin':' Hall. Large and 



robust variety. Whiteaves 1880. Geol. .Surv. Canada, Rep. Progr. , 



1879-80, p. 57. 

 Streptelasma robustum, Whiteaves 1896. Canad. Rec. Sc, vol. VI., p. 391. 



" Corallum simple, elongate conical, usuallj' rather strongly curved, 

 though some specimens are not so much curved as others, very large 

 for the genus, attaining to a length of seven inches as measured along 

 the curve of the convex side, to a height of nearly five inches, and to a 

 breadth or width of nearly two inches and a quarter at the summit. In 

 some adult or nearly adult specimens the sides are so much compressed 



