311 



they are only incipiently developed. The two genera may be thus distin- 

 guished : -in Maclurea, the aperture is entire, and the whorls usually 

 large ; but in Opliileta, it has a sinus below, and a notch above, while the 

 whorls are usually slender. 



All the species of Pleurotomoria and Helicotoma, of the Lower Silurian 

 rocks of Canada, of which perfect specimens have been found, have this 

 same form of aperture. And so have some of the Euomphali of the 

 Devonian and Carboniferous rocks. 



It would appear also that Madurea is a dextral shell, and that the flat 

 side is the umbilicus. 



Locality and Formation. This species occurs at Bedford, in Stan- 

 bridge, range 6, lot 20 ; in Farnham, range 5, lot 41; and at Cow Head, 

 in Newfoundland, in Division P; Quebec group. 



Collectors. T. C. Weston, J. Richardson. 



HETEROPODA. 

 BELLEROPHON PALINURUS. (N. sp.) 



Fig. 302. 



Fig. 302. Bellerophon Palinurus. Side and front views. The specimen figured, 

 being imperfect, does not show the form of the lip. 



Description. Sub-lenticular ; dorsum acutely carinated ; greatest 

 width close to the umbilicus ; vertical diameter from one inch to one inch 

 and a half. The outline on a side view is elongate ovate, the. vertical 

 diameter (from the upper side of the aperture through the umbilicus) 

 being usually one-fourth greater than the horizontal diameter, and often 

 more owing to a distortion to which the species seems to be subject. The 

 greatest convexity is close to the umbilicus, whence the surface ascends, at 

 first with a convex, and then with a concave slope to the dorsal edge. The 

 latter is usually very acute, but in many specimens, it is minutely rounded 

 but always with a concavity, of variable width, just within. The umbilicus 

 is small, from one-sixth to one-fifth the horizontal diameter, rounded on the 



