OCTOQONAL. 219 



7. Tellina. An anterior fold in the ventral margin ; lateral 



teeth. Pig. 105, 106. 



8. Tellinides. No anterior fold; no lateral teeth. Kg. 



107. 



9. DoNAX. Margin denticulated ; shell wedge-shaped. Pig. 



108. 

 10. Capsa. Margin not denticulated, no lateral teeth. Fig. 

 109. 



OBELISCUS. Humph. Pyeamidella (part.) Lamarck; 



OBLIQUE, {pbliquus, lat.) In a slanting direction. The 

 whorls of spiral univalves generally take an oblique direction in 

 reference to the imagiaary axis of the shell. A bivalve is said 

 to be oblique when it slants off from the umbones. An example 

 of this is seen in Avictda, fig. 163. 



OBSOLETE, {pbsoletus, lat.) Worn out, out of use. This 

 term is used to express an indistinctness of character, which 

 sometimes results from the action of sea-water upon unpro- 

 tected parts of the shell, and sometimes from the deposits of 

 enamel formed in age, and covering the early striae, ribs, teeth, 

 &c. thereby rendering them less acute. 



OBTUSE, (obfusus, blunt.) The application of this term is not 

 peculiar to conchology. It is most frequently used to express 

 the character of the spire. Ux. The apex of Megaspira, fig. 294. 



OCEAJN'US. Montf. (" Come d'ammon vivant," Pr.) Nait- 

 TiLTJS umbilicatus, Auct. 



OCTHOSIA. Eanz. Clitia, Leach. 



OCTOCEEA. Bl. The first family of the order Cryptodibran- 

 chiata, Bl. containing the genus Octopus. A species of which 

 being found in the Argonauta, or Paper Sailor, has given rise 

 to the long continued controversy as to whether it is really the 

 constructor of the shell, or whether it is a mere pirate, and 

 having destroyed the true animal of the Argonaut, has possessed 

 itself of the habitation. This question is now set at rest. See 



AEaOKAUTA, 



OCTOGONAL. (petogonum.) Having eight angles. Por a;n 

 example, see Dentalium, fig. 2. 



