TRANSACTIONS OF WAGNER 

 I 344 



TERTIARY FAUNA OF FLORIDA 



species. The presence of these strong and extensive muscles, combining with 

 a well-developed ligament or resilium to steady the valves in their mutual posi- 

 tions, doubtless makes up for the absence of a strong dental armature or mar- 

 ginal serration in preventing injurious rotation of one valve on the other. The 

 mantle in this family is more closely adherent to the disk over its whole sur- 

 face than in most bivalves, and in many species is permanently attached by 

 small areas producing a system of punctuations of the shell over the disk. 

 Sometimes, indeed, larger irregular areas become attached and leave a perma- 

 nent impression on the shell. But these are individual mutations of no sys- 

 tematic import. A ramification of the genital organ, when swollen with ova, 

 often leaves an oblique sulcus across part of the disk which is very generally 

 present in the more heavy-shelled Lucinidcz. The peculiarities of the gills in 

 this group have already been alluded to (pp. 505, 544), and the very general 

 feature of an elongated, club-shaped, or cord-like foot. The latter, however, 

 is a character which varies in different members of the family as it does in the 

 Diplodontidce. Thus in Jagonia the foot is nearly normal and but moderately 

 elongated in Codakia, while in Phacoides and Lucina it is much elongated. 

 There are no siphons properly so called in the Lucinida. Their place is taken 

 by simple orifices in the posterior margin of the mantle. The little organ 

 usually alluded to as the " valve" of the anal siphon, and which is distinguished 

 from the siphon by being introvertible, occurs in many groups of Pelecypods. 

 In Lucinidce, however, it is developed to an extraordinary extent and takes 

 the place of a siphon for the exhalent orifice. Being usually introverted and 

 greatly contracted in alcoholic specimens, it is often overlooked, but occurs in 

 all groups of the family I have been able to examine. 



Genus CODAKIA Scopoli. 



Codakia Scopoli, Intr. ad Hist. Nat., p. 398, 1777. Type Chama codok Adanson, Senegal. 

 Lentillaria Schumacher, Essai, p. 147, 1817. Type Venus punctata L. (Chemnitz, Conch. 



Cab., vii., p. 15, pi. xxxvii., fig. 397, 1784). 

 Orbiculus (sp.) Megerle v. Miihlfeld, Mag. Ges. Naturf. Freunde zu Berlin, p. 58, 1811 



(not Orbicula Lam., 1799). 



Lenticularia Gray, P. Z. S., 1847, p. 196; error for Lentillaria Schum. 

 > Jagonia Recluz, Melanges Malac., p. 14, 1869; Actes Soc. Lin. de Bordeaux, xxvii., p. 



39, 1870. Type Le jagon Adanson = Venus orbiculata Montagu. 

 >Ctena Morch, Mai. Blatt., vii., p. 201, 1860; Codakia pectinata Carpenter. 

 Antilla de Gregorio, Bull. Soc. Malac. Ital. (Pisa), x., p. 217, 1885. Type Venus tigrina 



L. ; not Antillia Duncan (corals), 1864. 

 Codokia Fischer, Man. de Conch., p. 1143, 1887 = Codakia em. 



