230 ROYAL SOCIETY OF CANADA 



It seems altogether probable that the two represent only different 

 stages of preservation of one species. Other specimens might be re- 

 corded as Stropheodonta cavumbona, Hall; but most of theon are prob- 

 ably another condition of preservation of the same species. All three 

 forms are reprelsented in the St. Helen's collection. 



A specimen, partially exfoliated, closely resembles the figure le of 

 Plate 21, called "a partial cast of the ventral valve" of Stropheodonta 

 cavumbona " and may bo listed vmder that name. Its dimensions are 

 29 mm. wide at hinge margin and 24 mm. long; faint indications of 

 the muscular scar are as in the fignire cited/ and the lineations are 

 rather sharp and strong and show no indication of the intermediate 

 fine lines described as sometimes appearing on that species. 



16, Strophonella cf. Leavenworthana, Hall. 



Another specimen having the surface lineation of 8. continens is 

 nearly flat till near the front where it suddenly flares upward. It is 

 apparently the cast of the interior of a ventral valve. This specimen 

 is produced at the front as in the ventral valve of 8. Leanenworthana. 

 It is too imperfect, however, to make the identification with that species 

 certain. The lineations are fine with an occasionally stronger one, and 

 the margin at the front is slightly puckered. The specimen is r^erred 

 tentatively to 8. cf. Leavenivorthana. 



17. Orthis (Orthothetes) deformis, Hall. 



To this species are referred several specimens vn\h the surface 

 Btriations and the irregularity of surface form of both pedicle and dorsal 

 valves of Orthothetes. There are no specimens showing the extreme 

 elevation of the point of beak of pedicle valve of Hall's specimens figured 

 as 3a and 3b on Plate 15. But smaller specimens with twisted distorted 

 beak are in the series. Other specimens of similar surface lineations 

 and witli the convex (but irregularly convex) dorsal valve are included 

 under this name, recognizing the extreme degree of irregularity of the 

 species of this genus whenever occurring in quantities. Clarke 2 refers to 

 similar specimens, vox luu^e regular in form than ours, under the name 

 "Orthothetes (Schuchertella) Woolworthanus, Hall, mut. gaspe.nsis 

 nov." and coming from the Grande Grève limestone. 



In the collection are specimens which resemble the dorsal valves of 

 Hall's Orthis eminens, and from the distortion of the surface might 

 again be placed with " Orthis strophomenoides " (the surface only being 

 in evidence). These are included in this reference to Orthothetes 

 deformis after comparison on the ground that they are variations of 

 this very flexible species. 



1 Hall, J., Pal. N.Y.. Ill, Pt. 2, 1861. PI. 21, Fig 16. 



~ Early Devonic History, /-tc, 1908, p. 199, PI. 14, Figs. 9-14. 



