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1483 



TERTIARY FAUNA OF FLORIDA 



of external sculpture. As the type of the hinge-formula does not change, it 

 will be inferred that these distinctions are not of great weight. 



Geologicall)' the group is an old one ; in America typical Astartes occur in 

 the middle portion of the Comanche series of the Texas Cretaceous, but whether 

 certain Paleozoic forms which have been called Astarte really belong to the 

 genus or not is somewhat uncertain. 



Genus LIRODISOUS Conrad. 

 Lirodiscus Conrad, Am. Journ, Conch., v., p. 46, 1869; type Astarte tellinoides Conrad; 

 Tryon, Struct, and Syst. Conch., iii., p. 227, 1884; Fischer, Mau. Conchy!., p. 1016, 

 1887. 



Shell solid, subelongate, inequilateral, equivalve ; the nepionic valves flat, 

 usually concentrically ridged, the later portion of the disk more convex ; liga- 

 ment normal, external ; resilium separate, situated between the beaks, external 

 but with its base partly immersed and encroaching on the upper part of the 

 cardinal teeth ; dental formula ^- Q'-™"-" ; the left anterior lateral represented 



' R. lo.oioi.io 



by the bevelled edge of the valve and soinetimes indistinct; cardinals trans- 

 versely striate laterally ; inner margins crenate ; adductor scars rounded with 

 elevated margins. Type Astarte tellinoides Conrad, Claibornian Eocene {-\- A. 

 Nicklini'Lea and A. sulcata Lea, 1833, not Da Costa, 1778). 



This genus is characteristic of the Eocene and appears in the Midwa3'an as 

 L. subpontis and mediaviiis Harris ; in the Chickasawan as L. smithvillensis 

 Harris; and at Wood's Bluff, Alabama, in Clarke County, Mississippi, and 

 Lee County, Texas, as L. protractus O. Meyer typically of the lower Clai- 

 bornian; in the Claibornian it is represented by L. tellinoides; and in the 

 Jacksonian by the following species : 



Lirodiscus Wailesii n. sp. 

 Plate 57, Figure 21. 

 Astarte paralis Conrad, in Wailes, Agr. and Geol. Miss., pi. xiv., fig. 2, 1854; S. I. Eocene 

 Checkl., p. 23, 1866; not of Conrad, Journ. Acad. Nat. Sci. Phila., 2d Ser., ii., p. 276, 

 pi. xxiv.. fig. 16, 1853 (Cretaceous). 



Jacksonian Eocene of Jackson, Mississippi, Vince's Bluff, Arkansas, and 

 Montgomery, Louisiana ; Burns, Harris, and Vaughan. 



Shell subovate, with high, flat, nearly smooth beaks, the remainder of the 

 disk finely, concentrically ribbed with narrow, rather elevated ridges and wider 

 interspaces; beaks pointed, prosogyrate ; lunule smooth, sublanceolate, rather 

 deeply excavated ; escutcheon longer, narrower, and less impressed ; posterior 



