168 



Silurian Fossils of Canada* 



Diameter of a specimen of the ordinary size fifteen lines ; thick- 

 ness in the centre seven lines ; width of that portion of the umbi- 

 licus which is formed of the last whorl three lines ; of the portion 

 included in the penultimate whorl one line and one fourth ; width 

 of aperture at the base eight lines ; height about the same. A 

 small specimen nine lines in diameter is four lines and a-half in 

 thickness at the centre ; umbilicus two lines wide ; aperture five 

 lines wide at base and the same in height. 



Locality and Formation. — This species occurs at Pauquettes 

 Rapids in the Black River and Birdseye Limestone and also at 

 Lake St. John at the same level. 



Collectors. — Sir W. E. Logan. T. Richardson. 



Bellerophon disculus. N. s. 



Fig. 11. Fig. 12. Fig. 13. 



Fig. 11. — Bellerophon disculus. Front view. 

 12. — Bellerophon Argo. Front view. 

 13. — Side view of the latter. 



Description. — Lenticular ; compressed ; greatest thickness at the 

 umbilicus about one fourth the diameter ; the dorsum acutely ? 

 angular ; the sides gently convex next to the umbilicus, becoming 

 somewhat flat or very slightly concave towards the circumference. 

 Whorls two or three each concealing rather more than half 

 of the one next preceding it. Umbilicus small exposing all the 

 whorls in a series of rectangular steps. Aperture triangular, not 

 expanded, indented on the ventral side to about one third its height 

 by the preceding whorl ; the two sides gently convex uniting at 

 the dorsal angle at an angle of about 50°. Surface apparently 

 nearly smooth. 



Diameter of the only specimen examined one inch ; thickness at 

 the umbilicus three lines ; width of umbilicus four lines. 



