CANADIAN FOSSILS. 19 



in sandstones and conglomerates which must have been formed in a 

 shallow sea. They appear to have inhabited however every kind of 

 sea-bed (though more abundant in those of a sandy character), and 

 are common throughout the limestones of the New York and 

 Canadian series. 



It is probable that the angular-whorled and strongly-striated 

 species belong to a different genus from the elongate, beaded forms. 

 But they are at present kept together under one name, as sub-genera. 



M. bicincta, Hall. 



Plate IV. Figures 5, 6 (and 7 junior). 



Specific characters. — M. pyramidata, biuncialis, anfractibus 6-7, acuti- 

 angulatis (valde distinctis), laevigata — carind primarid crassd trili- 

 neatd suprd medium anfractus — secondrid obtusd ad suturam positis ; 

 umbilico parvo ; ore ovato effuso. 



Synonym. — M. bicincta, Hall, Palaeontology of New York, vol. i.j 

 plate 38, fig. 5. [M. perangulata, ib., plate 10, fig. 4, junior.] 



The shape of this common and fine species is rather abruptly but 

 regularly pyramidal, the spire composed of six or seven whorls, each 

 sharply angulated in the middle, or rather beneath the middle in the 

 whorls of the spire, but considerably above it on the body-whorl". 

 The keel is thick and prominent, ornamented with three faint-raised 

 threads, one along the middle. 



Beneath the principal carina a second, much less prominent and 

 obtuse, abuts against the suture (in the spire), and occupies a position 

 rather below the middle of the body-whorl. The slope of the whorl 

 above the principal keel is nearly straight, not concave ; between 

 the principal keel and the lower one a little concave, and beneath 

 the last the whorl is convex as far as the small umbilicus. The 

 mouth is ovate, gently effuse at base, and the columellar lip straight 

 and reflected, but apparently not closing the umbilicus. 



The surface, unlike that of most of the accompanying species, is 

 smooth ; the lines of growth obscure, but a good deal bent back. 

 The triple keel is not serrated or even decussated by them, but quite 

 even- edged. 



M. perangulata, Hall, has a more elongate spire, but does not 

 appear to differ specifically from young specimens of M. bicincta. 

 Those from Canada are more like what Prof. Hall has figured from 



