12 CANADIAN FOSSILS. 



Section Hormotoma. 



Elongate, beaded forms, like Hulojjella, but with a distinct band 

 and notch, as in the other Murchisonia. Mouth rounded, not effuse. 



M. gracilis, Hall. 



Plate V. Figure 1. 



M. elongata, biuncialis, anfractibus 10—13, ventricosis, rotundatis (supra 

 vix planulatis), cingulo centrali lato, etiam quartam, partem avfractus 

 cBquante. 



Synonym. — Hall, Palaeontology of New York, volume i., plate 39> 

 figure 4; page 181. 



This gracefully-formed species belongs to a group of Murchisonice, 

 which doubtless ought to be separated generically from the more 

 typical angulated forms. They resemble Holopella, McCoy (the 

 so-called Turritella of the Silurian rocks), in the elongate, beaded 

 form, and round, instead of oblong and effuse, aperture. The band 

 however effectually distinguishes them. The inner lip, too, is 

 reflected on the columella, which is probably not the case with 

 Holopella. 



M. gracilis is a fine species, full two inches long, and very gradu- 

 ally tapering ; of about twelve or thirteen round whorls, which are 

 only very slightly flattened on the upper side, above the band. 

 The latter is broad, equal to about one-fourth the whole width of 

 the whorl, and placed centrally or a very little below the centre. 

 (" On the centre," Hall.) The striae, which are close but not 

 prominent, curve sharply backward to this band, and forward again 

 beneath it. 



The slight angularity of the whorls is alluded to by Prof. Hall, 

 who compares it in this respect with the larger species, M. bellicincta^ 

 of the same limestone. This slight angle does not however detract 

 from the general roundness of the volutions, as represented in the 

 figures above referred to. It is an exceedingly plentiful species. 



Our figured specimen has the outer portion of the last whorl bro- 

 ken away so much that the inner lip (a) looks far more conspicuous 

 than it is in reality. It is slightly reflected over the columella. 



Locality. — Abundant in the slabs of limestone at Pauquette's 

 rapids, etc. 



