CEISTTEAL. 103 



the other anterior, elongated ; epidermis thick ; internal surface 

 pearly. Lamarck, in describing this shell, states, that he regards 

 it as intermediate between Trigonia and Unio. It should, how- 

 ever, certainly have been placed in the family of " Nayades," and 

 perhaps should form a part of the genus Unio itself. C. am- 

 bigua. Lam. PL vii. fig. 140. 



CATILLUS. Brong. Inocbramtis, Sowerby. Catilltts. Humph. 

 1797. CiMBEE. Montf. 1810. JSTayicella. Lamarck, 1822. 

 PI. X. fig. 158. 



CATOPHEAGMUS. Sow. (Erom Karw, beneath; (ppayfxoc, a 

 place paled in.) Order, Sessile Cirripedes, Lam. — Bescr. Eight 

 principal valves, cemented side by side in a circle ; eight small 

 pointed valves beneath, covering the joints of the upper circle, 

 and numerous still smaller valves forming the base of the shell; 

 operculum, four valves. — Obs. Catophragmus is the only genus 

 of SessUe Cirripedes, which consists of eight principal valves, 

 excepting Octomeris. The latter genus has not the accessary 

 pieces from which the former derives its name. C. imbricatus. 

 PL i. fig. 23. 



CAUDAL CAISTAL. The elongated hollow process which termi- 

 nates the aperture anteriorly of some univalve shells. Por in- 

 stance, Murex Haustellum, fig. 396, has an elongated caudal 

 canal. 



CELLANTHUS. Montf. Vorticialis, BL A genus of mi- 

 . croscopic Poraminifera. 



CELLULACEA. BL The second order of Cephalophora, BL 

 consisting of doubtful microscopic bodies, vdth a number of 

 variously arranged shells, as distingiushed from the true Poly- 

 thalamia, BL or chambered shells. See Poraminieera. 



CEMOEIA. Leach. 1819. A small patelliform shell, difiering 

 from KssureUa, in having the fissure placed behind the apex, 

 which is produced, pointed and incurved. It is the Patella 

 Pissurella, MtiU. Patella JSToachina, Chemn. P. Noachina, Sow. 

 Puncturella, Lowe. Scotland and Tierra del Puego. Cemoria 

 Plemingii, PL xiii. fig. 244. 



CENTEAL. A term used to indicate the position of the muscular 



