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1081 



TERTIARY FAUNA Oh . LORIDA 



line and not oblique. However, they are so similar as to be very interesting. 

 According to Turton and Hanley, the young C. echinatum is probably the C. 

 ciliare of Linne. 



Cardium ctenolium n. sp. 

 Plate 40, Figure 13. 



Oligocene sands of Oak Grove, Santa Rosa County, Florida ; Burns. 



Shell rounded, a little produced behind, with inflated beaks, subequilateral ; 

 sculptured with eighteen broad, rounded ribs separated by narrower flat inter- 

 spaces sharply defined ; there are posteriorly some fine radial striations and 

 over the whole shell fine concentric sculpture which seems stronger where 

 it passes over the ribs, especially distally, and in some places approaches im- 

 brication ; there is a small smooth area above the outermost anterior rib, but 

 none behind the beaks ; internal margins deeply fluted and radially striate ; 

 hinge normal. Lon. 19.5, alt. 18.5, diam. 14 mm. 



Although not spiny I have placed this species in the typical section, as in 

 all other characters this seems closely related to the true Cardia, and the latest 

 representative of that group known from our Tertiaries. 



Cardium acrocome n. sp. 



Plate 48, Figure 2. 



Oligocene marl of the Chipola River, Calhoun County, Florida; Burns. 



Shell small, rotund, plump, nearly equilateral, with moderately full um- 

 bones ; sculpture of about forty-five close-set, low, nearly flat radial ribs sepa- 

 rated by very narrow channelled interspaces; the alternate ribs anteriorly 

 surmounted with prominent hollow spines usually truncate at the ends, their 

 alternates showing low A-shaped spines; behind the middle of the shell the 

 long-spined ribs are less numerous and on the posterior area nearly all the 

 ribs have low spines; there is no smooth area near the hinge-margin; in- 

 ternally the margins are fluted or serrate minutely, and the shell radially sul- 

 cate near the margin ; hinge normal, delicate. Alt. 7.5, lon. 7.5, diam. 6 mm. 



Only a single valve of this very distinct little species was obtained. Owing 

 to the alternation in the sculpture it has somewhat the aspect of Criocardium. 



Subgenus TRACHYCARDIUM Morch. 



The only Eocene representative of this group is C. bellum Conrad (1875, 

 in Kerr, N. Car. Rep., App.), which has not been figured or sufficiently de- 



