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1287 



TERTIARY FAUNA OF FLORIDA ' 



Marcia (pars) H. and A. Adams, Gen. Rec. Moll., ii., p. 423, 1857 (no type selected) ; 



Chenu, Man. Conch., ii., p. 81, 1862 (V '. undulosa Lam.) ; Tryon, Syst. Conch., iii., 



p. 178, 1884 (V. undulosa Lam.); not Fischer, Man. de Conchyl., p. 1086 (Venus 



exalbida Lam.), 1887. 

 Leukoma Romer, Krit. Unters., p. 17, 1857, V. granulata Gmelin (not Leucoma Stephens, 



1829, Lepidoptera) ; Malak. Blatt., xiv., p. 92, 1867. 

 Leucoma Stoliczka, Cret. Pel. India, p. 148, 1871 ; Fischer, Man. de Conchyl., p. 1084, 



1887; not Leucoma Stephens, 1829. 

 <^Murcia Romer, Krit. Unters., p. 16, 1857; Mai. Blatt., xiv., p. 28, 1867; not Murcia 



Koch, 1835, Arachnida. 

 Anaitis Romer, Krit. Unters., p. 16, 1857; no type selected; Stoliczka, Cret. Pel. India, 



p. 149, 1871 ; Fischer, Man. de Conchyl., p. 1084, 1887, V. paphia L. ; not Anaitis 



Duponchel, 1829, Lepidoptera. 

 Chione Deshayes, Cat. Conch. Brit. Mus., i., p. 118, 1853 ( m five sections) ; H. and A. 



Adams, Gen. Rec. Moll., ii., p. 420, 1857. 



This group contains solid trigonal shells which have three cardinals in 

 each valve and (excepting a few aberrant species) have the valve margins 

 entirely crenulate; all have a small triangular sinus, a lunnle circumscribed 

 by an incised line, an escutcheon not limited by any line and defined chiefly 

 by a deficiency of coarse sculpture and a more or less pronounced ridge radi- 

 ating from the beak towards the posterior margin. The ligament, though 

 inset, is usually visible externally ; some of the central cardinals may be 

 grooved or bifid ; rugosities appear on the hinge in a few instances. The 

 sculpture is variable, chiefly comprising concentric ribs or lamellae and less 

 prominent radials. 



A few, mostly small forms, have the concentric sculpture less prominent 

 than the radial. The lamellae are often expanded into elegant leaflike processes 

 distally. In a number of cases the right posterior dorsal margin is grooved 

 to receive the bevelled edge of the opposite valve behind the hinge-plate. In 

 Gomphina alone is any trace of a corresponding grooving anteriorly. The 

 genus may, for convenience, be divided into a number of groups, as follows : 



Subgenus Chione s. s. Type C. canccllata Linne. 



Sculpture of radial ribs decussated by concentric, sharp, elevated lamellae; 

 the dental formula is L - IOIOI -, the teeth are usually entire and smooth or feebly 



R. oioioi. 



channelled. The siphons are short and partly separated. 



Section Chione s. s. Type C. cancellata Linne. 



In a few of the larger species, like C. gnidia, a feeble fourth cardinal is 

 barely perceptible below the ligament of the right valve and almost coalescent 



