CANADIAN FOSSILS. 15 



The upper surface of this variety is concave, not flat. 

 Locality. — Alluinette Island, in siliciferous limestone. 



H. spinosa, N. sp. 



Plate II. Figures 9, 10. 



H. vix semhincialis, anfractibus 4—5, paullo elevatis, extus carinatis, supra 

 plants seu sub-concavis tuberculisque cristatis sparsis, sub his convexis ; 

 umbilico angusto verticali ; ore sub-rotundo. 



Whether the spinose ornament be considered structural or extra- 

 neous, this is certainly very distinct from all the varieties of the last 

 species, and more elegant in outline. The shape of the deep umbilicus, 

 with its vertical sides, is a good deal like that of H. larvata next 

 described, but the form of the shell is much more depressed. 



The upper surface is rather thickly studded over with tubercles, 

 which are disposed in sub-concentric rows, one row of large com- 

 pressed crest-like tubercles along the outer carina, an imperfect row 

 within this on the upper concave surface, and several incomplete 

 rows of smaller size on the outer convex edge. All have an irregular 

 appearance, and it is more than probable are only the relics of a 

 papillate sponge, converted into silex, and having its projecting 

 portions determined in position by the ridges of the shell. 



H. LAEVATA, N. sp. 



Plate II. Figure 11-14. 



H. semhincialis, Icevigata, spird lente elevatd ; anfractibus 5, supra sub-con- 

 cavis, subtus convexissimis ; umbilico verticali angusto : ore rotundato 

 margineque acuto valde sinuato. 



This shell is covered so frequently with a coat of the sponge, 

 Stromatocerium rugosum, as to suggest the specific name. The upper 

 side or spire only is covered, just as the Halichondria panicea invests 

 the Buccinum and other common univalves of the British coasts. 

 (See Johnston's "British Zoophytes," 1st edition.) 



Some specimens however, which are free from the parasite, shew 

 the spire to be composed of five gradually increasing whorls, each 

 about one and a-half times the width of the preceding. The whorls 

 are slightly concave on the upper side, which is divided by an 

 angular ridge from the convex outer border. The base is regularly 



