[WILLIAMS] FOSSIL FAUNAS OF THE ST. HELEN'S BRECCIAS 225 



but from one of the specimens, in which one side is entire wliile on 

 the other the shell is removed, they are fomid in this respect to be 

 identical with the shell above referred to as S. ctimherlandiœ, which leads 

 to the conclusion that the two species are one species, Sp. gaspensis 

 standing for the forms whicli are expressed by the specimens of the 

 eastern province, while Sp. cumheiiandiœ is the Maryland type, both 

 types finding a place in the St Helen's fauna. 



19. Spirifera cycloptera, Billings, not Hall {? Sp. trihulis. Hall). 



I have given this label to a small imperfect pedicle valve (which, 

 when entire, was apparently about 22 mm. broad by 16 mm. long,) as 

 evidently representing the smaller of the forms described by Billings as 

 "Spirifera cycloptera" and figured as éb and 4c of Plate Ilia of 

 Paleozoic Fossils, Vol. II, 1874. 



Six rounded plications can be counted on the sides, although the 

 surface is exfoliated; these appear to have been distinct lamellose 

 ridges which may well have been marked by the fine inteiTupted lines 

 in perfect specimens. Another specimen is intermediate between Hall's 

 S. cycloptera and /?. trihidiè. 



WJitvther S. cycloptcru^, Hall, varies so as to cover both forms de- 

 scribed by Billings is a question more of interpretation than of fact. 

 In the specimens identified by Billings under the name S. cycloptera 

 are extremes including forms such as Hall called *S'. tribulis. The forms 

 in the St. Helen's limestone (252.1) are intermediate between the 

 specimens figured and described by Billings under the name Spirifera 

 cycloptera. (Hall).^ 



21. Metaplasia pyxidata, Hall. 



A single imperfect specimen of normal size of Metaplasia pyxidata. 

 Hall, a pedicle valve, showing the median sinus and a faint plication on 

 each side, is referred to this species. The internal characters are not 

 evident. The only other species with which it can be compared is the 

 M. disparali>s, Hall of the Comiferous; but it differs from that species 

 by its smaller size, less prominent umbo and the less prominent and 

 single lateral plication. Thus, on the hypothesis that the latter species 

 is an evolved descendant of Metaplasia pyxidata, the St. Helen's speci- 

 men bespeaks an Oriskanian rather than Onondagian horizon. 



22. Modiomorplia {cf. concentrica) , Helena, var nov. This is a 

 small shell having the general form and surface markings of Modio- 

 morplia concentrica, but narrower and more elongate and the anterior 

 wing narrow and more produced forward from the umbo. The angle 

 made by the cardinal slope anterior to the umbo with the cardinal 



1 Paleozoic fossils, Vol. II. Pt. 1, 1S74, p. 4S. Plate 3a, figures 4, 4a, 4b, 4c. 



