GASTEROPODA. 
from it; the aperture is contracted, and the upper angle of 
each lip bears a more or less distinct tooth. 
Distribution, 2 species, Great Oolite.and Coral Rag, France 
and Germany. 
Sub-family—BELLEROPHONTINZ. : 
Genera :—PORCELLIA (p. 844), BELLEROPHON (p. 344) (with 
Bucania), and 
TREMANOTUS, Hall, 1863. 
Type, Bucania Chicagoensis, M‘Chesney. 
Shell thick, aperture dilated; having the form of Bucania, 
but with a row of isolated oval siphonal openings along the 
middle of the dorsal side. 
Fossil, 2 species. Upper Silurian, North America. 
? CARINAROPSIS, Hall. 
Shell haying a patelloid aspect. Spire usually attenuated ; 
body whorl expanded abruptly ; cavity shallow, presenting a 
kind of septum as in Crepidula. 
Fossil, 2 species. Silurian, America. 
FamMIty XJ,.—FISSURELLIDA. 
DESLONGCHAMPSIA, M‘Coy, 1850. 
Dedicated to Dr. Eudes Deslongchamps, the renowned French 
paleeontologist. 
Type, D. Kugenei, M‘Coy, Mor. and Lye. 
Shell patelliform, apex acute excentric; with a wide longitu- 
dinal anterior sulcus, produced into a rounded lobe. 
«This genus differs from Metoptoma in its ornamented surface, 
and the front margin being produced downwards into a 
rounded lobe. This latter structure would prevent the firm 
adhesion of the shell.” —(M‘Coy.) 
Fossil, 3 species. Lower Volites. England, Normandy, 
Galicia. 
FAamMIty XIII.—PATELLIDA. 
HELCcION (Montfort, p. 278), Jeffreys. 
Etymology, a breast-collar. 
Synonyms, Nacella, Schumacher; Patina, Leach; Calyptra 
(pars), Klein. 
Example, H. pellucidum, (Patella pellucida, Linné). 
Shell semioyal, not resembling a peaked hat as in Patella; 
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