128 COSTELLAUIA. 



COEONTJLA. (Corona, a crown, dim.) Order, Sessile Cirripedes, 

 Lam. Fam. Balanidea, Bl. — Descr. Six radiated valves, joined 

 side by side in a circle, forming a depressed cone ; internal struc- 

 ture of the valves, porous or chambered ; thickened at the base ; 

 operculum consisting of four valves in pairs ; imbedded horizon- 

 tally in a cartilaginous substance. — Obs. The shells composing 

 this genus are found partly imbedded in the skin of whales, and 

 the shells of tortoises, and are therefore destitute of the shelly 

 foundation on which the Balani and other Coronular Multivalves 

 are supported. C. Testudinaria, (CnELOisroBiA, Leach,) fig. 15. 

 C. Balaenarum, (Cetopietts, Eanz.) fig. 16. C. Diadema, (Dia- 

 DEMA, Eanz.) fig. 17. PL i. fig. 15, 16, 17. 



COEONULAE MULTIYALYES are those which have their pa- 

 rietal valves joined together side by side in a circle, surrounding 

 the body of the animal, so as to form a sort of coronet. This is 

 the characteristic of the Sessde Cirripedes of Lamarck's system, 

 the Balanidea of De Blainville. 



COEEODED. (Corrodo, eat away, consume.) The umbones, 

 apices, and other thick part of shells, are frequently worn away 

 or consumed by the action of the element in which they exist. 

 As the thickest parts of some shells are the most subject to this 

 operation ; it appears to the author to arise from the outer surface 

 of the shell, being less under the influence of the animal juices 

 than the other parts ; and therefore, more exposed to the influ- 

 ence of the surrounding element. This, however, is not the 

 case with respect to the Nayades and other fresh-water shells ; 

 with these, corrosion does not take place until after the thick 

 epidermis which covers them, becomes woimded by some means 

 or other, and then the animal thickens its shell within as fast 

 as it is corroded without. 



COETALUS. Montf. (Conch. Syst. 1. 115.) A genus of 

 microscopic Eoraminifera, placed by De Blainville in a division 

 of the genus Eotalites. 



COSTATED. Eibbed, as Cardium Angulatum, fig. 123. 



COSTELLAEIA, A sub-genus of the genus Tiara, Sw. (Mitra.) 

 C. rigida, Swainson, Zool. 111. 1st series, pi. 29. 



