Yol. 55.] ECTOMAETA. AND HORlfOTOMA. 261 



it, and I am uncertain of its having any claim to inclusion in 

 Bormotoma. The specimen figured in ' The Geology of Russia ' 

 by Murchison, De Verneuil, & Von Keyserling, vol. ii, p. 'S',i9 & 

 pi. xxii, fig. 7, from the (Upper) Silurian is also different : the 

 authors themselves doubt its identity with the Scandinavian species, 

 both on account of its much greater size and its prominent central 

 band, and if it should prove distinct they suggest the specific name 

 Demidorji. The form of the band and the less oblique lines of 

 growth distinguish it from Hormotoma. Schmidt also gives M. cin- 

 (julata, His., from the Obere (Esel'sche Gruppe (Upper Silurian). 

 The Fl. insignis, PI. exilis^ and Fl. bellicincta of Eichwald are all 

 from the Lower Stage (Ordovician ?). Fl, hijuc/ata, Eichw., from 

 the Middle Stage, may perhaps belong to Hormotoma, but the figure 

 and description are insufficient to determine this point. 



Prom Offley Island, in the Arctic Regions, a large species has been 

 recorded by Mr. R. Etheridge,' which he has named M. latifasciata. 

 An examination of the type-specimen convinces me that it should be 

 referred to Hormotoma, as it has the very oblique lines of growth 

 and characteristic band of that species. 



Two species of Hormotoma were given by Bigsby in ' Thes. Sil.' 

 p. 156, from the Gordon Isles (Tasmania,) namely, H. nerinoia, Salt., 

 and H. usitata, Salt. The names are only in MS., and the original 

 specimens are probably in the Tasmanian Museum, Hobart. They 

 were afterwards included in the ' Catal. Austral. & Tasman. Foss.' 

 by R. Etheridge, Jun., in 1878, and were also given in the lists 

 of Lower Silurian (Ordovician) fossils in the ' System. Ace. Geol. 

 Tasmania,' by R. Johnston, in 1888, but they were neither described 

 nor figured. 



In the United States and Canada there are numerous species of this 

 genus. Ulrich & Scofield ^ refer the following to it: — M. Anna, Bill., 

 M. simulatrix, Bill., M. Vesta, Bill., and M. gracilens, Whitf., from 

 the Calciferous Group ; M. Frocris, Bill., from the Black River Group ; 

 M. gracilis. Hall, H. subangulata, Ulr., H. SaHeri, Ulr., M. bellicincta, 

 Hall, H. trentonensis, Ulr., and 1 M. major. Hall (not M. major, 

 Whitf., which they consider identical with H. trentonensis), from the 

 Trenton and Cincinnati Groups ; and M. Hebe, Bill., from Gaspe. 

 They judge it best to place M. egregia, Bill., from the Gaspe Sandstone, 

 here, although they say the band is too low for it to be regarded as a 

 typical member of the genus. A consideration of the species described 

 in this paper will, however, show that the band varies in position. 

 M. agilis, Bill., from the Quebec Group, they also state may belong 

 here, but it is insufficiently known. Of M. teretiformis, Whiteaves, 

 they remark that it has all the characters of Hormotoma despite 

 its great size, and they believe it to be distinct from the species of 

 Billings described under that name. They regard M. angustata, 

 Hall, as a variety of M. gracilis. 



To the foregoing list must be added H. winni2^egensis, y^^hiteaves,^ 



^ Quart. Journ. Geol. Soc. vol. xxxiv (1878) p. 600 & pi. xxvii, fig. 1. 



2 Final Eep. Geol. & Nat Hist. Surv. Minn. vol. iii, pt. ii (1897) p. 1014. 



3 Geol. Surv. Can. ' Pal. Foss.' vol. iii, pt. iii (1897) p. 192 & pi. xxi, fig. L 



