GASTROPODA. 849 
Bucaniide. | 
description, especially the part which relates to the absence ofa slit and dorsal band, 
we place the genus near Owenella and Protowarthia, and consider it as well dis- 
tinguished from those genera by the trilobate character of its shells. Koken (Joc, 
cit.) without sufficient warrant considers Meek’s diagnosis as incorrect and proposes 
to extend the limits of the genus so that it will include, beside the species placed 
here by Meek and which Koken admits he has not seen, two other groups of 
species, one falling under our Tetranota, the other, having revolving surface 
markings, probably under Bucanopsis. For further discussions see remarks specially 
devoted to the genera named. 
Family BUCANIIDAL. 
Symmetric, involute shells; whorls rather numerous, merely in contact, or 
embracing slightly, all visible in the umbilicus; aperture often expanded abruptly; 
dorsal slit-band distinct, the slit itself generally very long and narrow, some- 
times represented by a row of openings; surface with transverse lamellz or lines, 
usually crossed at right angles by short ribs. 
TeTrRaNota, n. gen. (Bucania [part.| of Hall and other authors; Bucanella 
[part.], Koken, not Meek.) Shell thin; aperture moderately expanded, laterally 
chiefly; inner lip without callosity; sinus more or less deep, terminating in a short 
slit; whorls generally compressed so that the transverse diameter greatly exceeds 
the vertical; umbilicus open, large or of moderate size; dorsal band very wide, 
margined on each side by a strong ridge; about midway between these ridges and 
the narrowly rounded or angular sides of the volutions there is another ridge 
on each side, making in all four constant revolving ridges; aside from these the 
surface markings consist of rather delicate, sublamellose, regular lines of growth, 
each crossed at right angles by its own set of minute ribs. The revolving ridges, 
the lateral ones especially, are best developed on the inner whorls and may become 
quite indistinguishable near the aperture. Type, Bucania bidorsata Hall. 
T. macra U. & S. T. wisconsinensis Whitfield sp. | slaee 
T. sexcarinata U. & S. T. bidorsata Hall sp. «Sul exes Sulmien wOSSIS eel CONSE 
Gi igg LSaS | in this volume. 
Koxenta, n. gen. (Bucanella [part.], Koken, 1889, not Meek, 1570.) Volutions 
depressed; slit-band wide, flat, elevated, with a broad concave space on each side; 
umbilicus open, rather large; aperture not expanded, lips thin, the outer one deeply 
emarginated. Surface with straight, uninterrupted revolving ribs, strong on the 
lateral parts of the dorsum, fine on the slit-band; growth lines very delicate. Type, 
Bucanella esthona Koken (Neues Jahrbuch ftir Mineralogie, etc., Beilageband vi, p. 
389; 1889), Lower Silurian drift, Berlin. One American species, K. costalis U. & 8. 
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