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1527 



TERTIARY FAUNA OF FLORIDA "^ ' 



about the posterior third ; surface with numerous nearly concentric, subequal 

 ripples, fading out behind the vertical of the beaks and each about one milli- 

 metre wide. Length 33.5, height 19.0, diameter of right valve about 6.0 mm. 



A single well-preserved internal cast in a fine-grained limestone is in the 

 collection labelled as from Vicksburg, Mississippi, on the authority of J. B. 

 Marcou. It is more nearly like the average typical Thracia in form than are 

 the more recent Cyathodonta. 



Cyathodonta guadalupensis n. sp. 

 Plate 53, Figure 6. 



Oligocene of Guadeloupe Island, Lesser Antilles ; J. W. Spencer. 



Valves moderately convex, the left valve less so, the beaks high, nearly 

 median, the anterior dorsal slope rapidly descending, rounded near the base; 

 base arcuate, posterior end roundly subtruncate ; sculpture of prominent, nearly 

 concentric ripples subequally distributed except on the posterior dorsal slope, 

 where they are obsolete, an obscure radial sulcus near the posterior dorsal mar- 

 gin. Length 38, height 30, the beak about 20 mm. from the posterior end; 

 diameter of the right valve 10, of the left valve 6 mm. 



A single well-preserved internal cast was obtained. The following species 

 is very similar, but the proportions and sculpture differing in a marked way it 

 was thought best to treat it as distinct. 



Cyathodonta Spenceri n. sp. 

 Plate 53, Figure 8. 



Oligocene limestones of Guadeloupe Island, Lesser Antilles ; J. W. Spencer. 



Valves moderately convex, the right valve more so, the beaks low, at three- 

 sevenths the whole length from the posterior end ; anterior slope slowly de- 

 scending, terminally rounded; base arcuate; posterior slope convex, com- 

 pressed, the posterior end vertically subtruncate; a rounded radial ridge be- 

 tween two wide, shallow depressions extending from the beaks to the lower 

 posterior angle in the right valve ; sculpture of prominent ripples, with wider 

 interspaces, obsolete on the posterior dorsal slope. Length 43, height 32, 

 diameter of right valve 8, of left valve 7 mm. 



A single well-preserved internal cast was obtained. The sculpture is more 

 prominent and sparse, the anterior end proportionately longer, the beaks less 

 elevated, the posterior dorsal slope more compressed, and the valves more 

 nearly equally convex than in T. guadalupensis. 



De Gregorio figures a Thracia estiva, of which the provenance is uncertain. 



