16 



subelliptical, twice as long as high : anterior end regularly but narrowly 

 rounded, posterior end narrowing equally and rather abruptly at its 

 extremity both above and below and subangular or somewhat pointed 

 in the middle : superior border slightly convex in front, and descending 

 with an extremely gradual curve behind : basal margin broadly 

 rounded : beaks small, not very prominent, curved forwai'ds and placed 

 a little in advance of the mid-length. Surface marked with about 

 twenty or twenty-one regularly disposed, equidistant, concentric ribs. 

 Hinge dentition and muscular impressions unknown. 



Length, twenty millimetres : height ten mm. 



Elora, T. C. "Weston, 186Y: two moulds of the outer surface of the 

 shell. Durham, Mr. J. Townsend : one mould. The description and 

 figure are taken from a gutta percha cast of the mould collected by 

 Mr. J. Townsend. 



As the internal cha]:acters of this little shell are unknown, its generic 

 position is quite uncertain. It is only provisionally placed in Billings' 

 genus Ilionia. 



GASTEROPODA. 



SUBtTLITES COMPACTUS. (N. Sp.) 



Plate 3, fig. 2, and plate 7, fig. 6. 



Shell slender, subcylindi-ical or narrowly subfusiform, the length 

 being approximately rather more than three times greater than the 

 breadth : last whorl of the spire broader and more convex than any of 

 the others : suture lightly impressed : body-whorl narrower than the 

 preceding volution, at least in its dorsal aspect, cylindi'ical and some- 

 what constricted at and above the middle, decreasing unequally and 

 rather rapidly in breadth below : base apparently tmncated, with a 

 moderately deep siphonal notch, which is bounded posteriorly by an 

 oblique and not very prominently rounded keel, with a shallow depres- 

 sion behind it. Surface apparently smooth. 



Approximate length from twenty to twenty-two millimetres : maxi- 

 mum breadth six mm. Durham, Mr. J. Townsend. A single cast, 

 with the apex of the spire and a portion of the base broken off. 



This is a much smaller species than the Subulites ventricosus of Hall, 

 which is common in the Guelph Formation at Gait, Hespeler, Blora 

 and Durham, or than the S. terebrmformis of Hall and Whitfield, from 

 rocks of the same age in Ohio. Prom the former it differs also in its 

 much more slender contour, and from the latter in its shorter and 

 more closely coiled spii-e. 



