Yol, 55.] ECTOMAEIA AI^D H0EM0T05IA. 253 



are very indistinct, but on one individual they may be discerned on 

 tbe lower part of a whorl, where they agree with those of Ulrich 

 & Scofield's figure, op. supra cit. pi. Ixx, fig. 56, which evidently 

 is more perfectly preserved. 



E. NieszkowsJcii greatly resembles E. (?) pagoda in general form, 

 ornamentation, and in the lines of growth ; but the latter species 

 is smaller and more slender. As Koken's name has the priority, it 

 must stand. The only other species which he describes is E. Hr- 

 naensis: it has more evenly convex whorls and less prominent 

 ornamentation than the type. 



Eesemblances. — Ectomaria WlSlj he distinguished from Hormo- 

 toma by its possession of a shallower sinus which does not give rise 

 to a distinct band, and by the circumstance that its whorls are 

 ornamented by more prominent keels. It comes nearest to Hyper- 

 gonia, but in that section the sinus is situated above, instead of 

 on the widest part of the whorl. In AcUsoides the sinus is deeper, 

 and the whorls are more evenly convex. 



Range. — In the British Isles at present I only know of four 

 forms which probably belong to this genus : namely, E. pagoda 

 vars. Peachii and orientalis, E. girvanensis, and E. exigua- 



M'Coy (' Brit. Pal. Foss.' p. 292) refers a shell from the Lower 

 Bala of KnockdoUian, near Ballantrae, to Murchisonia angustata. 

 Hall. The fossil is much worn and too imperfect for accurate 

 determination ; but, so far as can be judged, it appears to have more 

 in common with members of this genus than with Hormotoma 

 angustata. Hall, which Ulrich & Scofield consider to be a variety 

 of H. gracilis. Hall. M' Coy's specimen gives evidence of two 

 rather strong keels on the lower half of each whorl. 



These are all from the Cambrian and Ordovician rocks of Scotland. 

 So far, I have not met with any well-authenticated species from a 

 higher horizon. 



As already mentioned, Ectomaria occurs in the Ordovician rocks 

 of the Baltic Provinces, where it is represented by two species, 

 according to Koken. 



In Canada there are Eimema prisca, Billings, from the Calci- 

 ferous Group, ^ and Eunema (?) pagoda, Salter, from the Black River 

 Limestone, both of which have also been described by Ulrich & 

 Scofield from the Stones River Group ; the former at Minneapolis 

 (Minn.), Dixon (111.), and Murfreesboro (Tenn.) ; the latter near 

 Cannon Tails (Minn.), and near Beloit (Wise). Whitfield refers 

 a shell from the Trenton Group of Wisconsin to E. (?) pagoda, 

 but Ulrich & Scofield consider it identical with E. prisca. 

 Whiteaves describes a form from the Galena and Trenton formation 

 of Lake Winnipeg, which he states is a variety of Solenospira 

 pagoda, Salt., and designates it occidentalis. Murchisonia Adelina, 

 Billings, from the Quebec Group of Canada, also probably belongs 



1 The Calciferous Group is by some regarded as Upper Cambrian, and by 

 others as Lower Ordovician ; the Stones Eiver, Black Eiver, Trenton, and 

 Quebec Groups belong to the Ordovician, the Hamilton to the Middle Devonian, 

 and the St. Louis to the Lower Carboniferous System. 



