GASTEROPODA. 345 
Fossil, 128 species. Lower Silurian—Carb. North America, 
Europe, Australia, India. The name Bucania was given by 
Hall to the species with exposed whorls; in B. expansus, Pl. 
XIY., Fig. 28, the aperture of the adult shell is much expanded, 
and the dorsal shit filled up. (Salter.) 
Bellerophina, D’Orbigny (not Forbes), is founded on the 
Nautilus minutus. Sby. Pl. XIV., Fig. 26, a small globular 
shell, spirally striated, and devoid of septa. Itis found in the 
gault of England and France. 
CYRTOLITES, Conrad. 
Type, C. ornatus, Pl. XIV., Fig. 30. 
Etymology, kurtos, curved, lithos, stone. 
_ Shell thin, symmetrical, horn-shaped or discoidal, with whorls 
more or less separate, keeled, and sculptured. 
Fossil, 13 species. Lower Silurian—Carb. North America, 
Europe. 
? Ecculiomphalus (Bucklandi), Portlock, Pl. XIV., Fig. 31. 
Lower Silurian, Britain, United States. Shell thin, curved, or 
discoidal with few widely separate whorls, slightly unsym- 
metrical, keeled. 
Fig. 142, Maclurea Logani (Salter), L. Silurian, Canada. 
? MAcLUREA, Lesueur. 
Named after William Maclure, the first American geologist. 
Shell discoidal, few-whorled, longitudinally grooved at the 
back, and slightly rugose with lines of growth; dextral side 
conyex, deeply and narrowly perforated ; left side flat, exposing 
the inner whorls; operculum sinistrally sub-spiral, solid with 
two internal projections (¢ #), one of them beneath the nucleus, 
yery thick and rugose. 
_ Fossil, 5 species. Lower Silurian. North America; Scotland 
(Ayrshire, M‘Coy). 
This singular shell abounds in the ‘‘ Chazy” limestone of 
the United States and Canada; sections of it may be seen 
eyen in the payement of New York; but specimens are very 
difficult to obtain. We are indebted to Sir W. H. Logan, 
of the Geological Survey, Canada, for the opportunity of 
Qa3 
