118 CONCENTEIC. 



3. CoLTJMBELLA. Outer and inner lips denticulated or granu- 



lated. Fig. 430. 



4. VoLTJTA. Outer lip thickened ; folds on tlie columella ; 



aperture generally wide ; apex papUlary ; including Sca- 

 phella, Harpula, Volutilithes, Cymbiola. Kg 433, 436. 



5. Melo. Shell comparatively light ; spire short, sometimes 



hidden ; apex round, spiral ; folds on the columella la- 

 minar, rig. 435. 



6. Ctmba. Upper edge of the aperture separated from the 



body whorl by a flat disc ; apex mammiUated, irregular ; 

 folds on the columella thick. Pig. 434. 



7. YoLTAEiA. Cylindrical ; aperture long, narrow ; folds on 



the columella small ; spire hidden. Fig. 439. 



COLTJS. Humphrey. 1797. Fusus Coius, Lamarck, and similar 

 species. PL xviii. fig. 387. 



COMPLAJSTAEIA, Swainson, 1840. A subgenus of Alasmodon, 

 (Unio), thus described, " shell winged ; the valves connate ; the 

 bosses very small and depressed ; cardinal teeth two or three ; 

 lateral teeth represented by irregular grooves. C. gigas (Unio), 

 Sow. Man. fig. 141. Alasmodon complanatus, (Say) C. Eu- 

 gosa, Sw." 



COMPEESSED. Pressed together, or flattened. The application 

 is the same as in common use. A Patella may be described as 

 a vertically compressed cone. A EaneUa, on account of the two 

 rows of varices skirting the whorls, appears, as it were, laterally 

 compressed. A bivalve shell is said to be compressed when it 

 is flat, that is, when only a small cavity is left in the deepest 

 part when the valves are closed. Perhaps the Placuna placenta, 

 fig. 184, is the most remarkable instance of this character. 



CONCAMEEATIONS. {Con, with, camera, a chamber.) A 

 series of Chambers joining each other, as in Nautilus, Spi- 

 rula, &c. 



CONCENTEIC. A term applied to the direction taken by the 

 lines, of growth in spiral and other shells, {longitudinal of some 

 authors.) Every fresh layer of shelly matter forms a new circle 



