66 THE ROYAL SOCIETY OF CANADA 



Spencer describes the species in the following terms: 

 "Shell large and broad, pyramidal; medial depression on side 

 scarcely apparent, but producing an abrupt bending of the striae. 

 Surface of shell removed, showing only the internal cast. Broad, 

 flattened, transverse ridges, separated by narrow deep channels, 

 cross the sides of the shell and bend abruptly at medial lines. These 

 are again traversed by shallow longitudinal striae situated closer 

 together than the transverse ridges, but which do not penetrate them 

 to a depth of the separating transverse grooves. But, where the 

 longitudinal striae cross the transverse channels there are punctures 

 in the grooves ; and where they cross the ridges there is a depression 

 in the centre of the ridges. 



"I have only seen one specimen, which is not entire. The fragment 

 is 13 centimetres long, with two sides partly remaining; the greatest 

 width at base of side (visible) is about five centimetres. In some 

 places the shell is crushed, bringing the ridges and grooves together 

 very closely in a wrinkled manner; and, where not crushed, the surface 

 presents a wrinkled appearance. There are ten transverse ridges and 

 furrows in one centimetre of length. The longitudinal striae and the 

 punctures in the transverse grooves are situated one-half millimetre 

 apart." 



The specimen in the possession of the Royal Ontario Museum 

 of Palaeontology was found in chert so flattened that its original 

 shape cannot be correctly determined. The surface ornamentation, 

 however, is well marked. 



A description of this specimen follows : 



Shell large, tapering uniformly, of moderate thickness. The two 

 edges of the flattened specimen represent the two opposite angles of 

 the original pyramidal shell and, therefore, two adjacent faces 

 are seen, which are divided by a slightly sulcate line. The apical 

 angle is 25 degrees. 



The general character of the ornamentation is as follows: Each 

 face is marked by transverse ridges which have a forward inclination 

 from the lateral margins and meet at an angle of 145 degrees along 

 the median line of the face. These transverse ridges are separated 

 by grooves of about twice the width of the ridges. The floor of the 

 groove is not simple but is marked by low, rounded elevations at 

 right angles to its direction. These corrugations are separated by 

 somewhat sharper depressions; their spacing is about half that of the 

 main ridges; and they are not continuous from groove to groove over 

 the summits of the ridges. 



