604 E. ETHEPJDGE ON THE PALAEONTOLOGY OP THE 



the spire, or obliquely conical ; spire small, loosely or irregularly 

 coiled ; volutions few, rounded, usually four, contiguous, the sutures 

 varying in individuals ; body- whorl large; peristome expanded and 

 entire, slightly sinuous; surface of shell finely striated, near the 

 peristome rather coarsely so, or lamellose and reflected backwards ; 

 columella not seen in any of the specimens ; the peristome appears 

 entire. 



Our species would belong to that division of Platyceras having the 

 whorls contiguous, not free. 



Hall's genus Platyostoma contains shells resembling these acrocu- 

 liiform and Pileopsis-like species. Dr. Coppinger collected these at 

 Bessels Bay. 



Loc. Bessels Bay, lat. 81° 6'. 



HETEROPODA (NTTCLEOBRANCHIATA). 



This order of Pelagic Mollusca is represented by two genera of 

 the family Atlantidee (Bellerophon and Maclurea) ; both are widely 

 distributed. The former genus is known to contain about 140 spe- 

 cies, ranging from and through the lowest Silurian rocks up to the 

 Carboniferous Limestone. Our two specimens of Bellerophon are 

 from the Upper Silurian of Bessels Bay. Seventy species occur in 

 the Palaeozoic rocks of North America and Canada alone, 150 in 

 Britain and Europe. 



The Atlantidaa are all provided with a well-developed shell, which 

 in the older genera was inflated or discoidal and symmetrical ; in 

 Maclurea the aperture of the shell was closed by an operculum. 

 Both Bellerophon and Maclurea occur in the series of fossils brought 

 home by Captain Eeilden — Bellerophon from Bessels Bay and Maclu- 

 rea from Cape Erazer, Cape Hilgard, and Cape Louis Napoleon. 

 Maclurea is associated with Meceptaculites in each locality, as well 

 as with the large specimens of Haly sites referred to in this commen- 

 tary. I can only determine one species of Bellerophon amongst the 

 ' Discovery ' collection made by Dr. Coppinger, the forms occurring 

 being, I think, the same — neither of them in good condition. 

 I notice them, but leave specific determination. 



These two heavy-shelled Nucleobranchs predominated in the 

 Silurian seas of America, Grinnell Land, and probably Greenland — 

 Bellerophon being the Bessels-Bay genus, Maclurea characterizing 

 the beds at Cape Louis Napoleon, Cape Hilgard, and Cape Yictoria. 



Genus Maclueea, Lesueur, 1818. 



Lesueur's genus is numerically well represented in the collection, 

 and probably by two if not three species. 



In the British Islands we know this shell only from the Lower 

 Silurian rocks, not ranging higher than the Caradoc (M. macrom- 

 phala, M'Coy), the Arenig and Llandeilo series being its chief hori- 

 zon. At Durness, the most northerly part of Sutherlandshire, N.W. 

 Highlands, M. Peachii occurs abundantly in beds that are equivalent 



