TRANSACTIONS OF WAGNER 

 1 172 



' TERTIARY FAUNA OF FLORIDA 



anterior end narrower ; external surface polished, smooth except for faint 

 incremental lines, shell inflated ; beaks low, the subtriangular prodissoconch 

 conspicuous ; hinge with a stout, conspicuous left cardinal and a more slender 

 prominent right cardinal ; thickening of the margin over the resilium feebly 

 developed in both valves, the anterior lamina obsolete in both ; scar of the 

 resilium large, short, scars of the adductors and pallial line normal. Lon. of 

 a medium-sized specimen 8.5, alt. 5, diam. 4 mm. A broken specimen still 

 measures 10 mm. in length. 



This species forms the next term in a series of which in M. ferruginosa 

 the laminae are partially obsolete in front, and in M. substriata they are dis- 

 tinctly developed though small. It recalls Sportella Whitfieldi, but has a 

 thinner shell and much more delicate hinge. Species of this type nearly bridge 

 the conchological gap between M ontacuta and Sportella. 



? Montacuta actinophora n. sp. 

 Plate 44, Figure 2. 



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



Shell small, rather compressed, subcjuadrate, the anterior end much the 

 longer ; basal and dorsal margins subparallel, anterior end evenly rounded ; 

 posterior end short, sloping above, rounded below; beaks small, low, the 

 nepionic shell conspicuous ; outer surface marked with somewhat irregular 

 incremental lines, smooth near the beaks, elsewhere closely, evenly, sharply, 

 radially striate, an obscure ridge extending from the beaks backward and 

 downward ; hinge-plate narrow, in the right valve with one prominent slender 

 cardinal tooth directed oblicjuel}^ forward in front of a narrow elongate sulcus 

 for the resilium obliquely directed backward below the dorsal margin ; in the 

 left valve on each side of the sulcus is a rather obscure lamina, the anterior 

 most prominent and longer, the posterior fitting under the posterior dorsal 

 margin of the opposite valve, the anterior into a socket above the right cardinal ; 

 interior of the valves smooth or faintly radially striate, the muscular im- 

 pressions large and rather low down, the pallial line simple and wide. Lon. 

 II, alt. 7.6, diam. 4.5 mm. 



This is an elegant shell which has the external aspect of Scintilla but a 

 different hinge. The teeth differ from those of typical Montacuta in the short- 

 ness of the shank of the cardinal " hook" and in the presence of a posterior 

 lamina in the left valve, but traces of the latter may be found in several of the 

 other species. But for the absence of any evidence of an external ligament 

 this species might be referred to Sportella. 



