ART. 22 MIOCENE GASTROPODS AND SCAPHOPODS MANSFIELD 41 



MARGIN ELLA (GIBBERULA) TRTNITATENSIS, new species 



Plate 6, fig. 8 



Shell small, ovate-cylindrical, solid, polished; spire about 0.2 

 inin. higher than outer lip; body whorl marked with microscopic 

 bands (color ?), and a prominent rounded sulcus about 1 mm. from 

 the anterior end. A heavy wash of callus overruns the spire and ex- 

 tends forward over the face of the body whorl to the anterior 

 sulcus. Aperture narrow, linear, with a reflected anterior canal 

 which emarginates the base of the whorl. Outer lip nearly vertical, 

 margin slightly inflected medially, moderately curved in below and 

 reflected above; serrated within below the margin. Columella pro- 

 vided with a strong oblique plication below the sulcus, and four 

 weaker, equally spaced, transverse plications above. Lower border 

 of inner lip provided with a thin, nearly erect plication. 



Dimensions: Type (U. S. Nat. Mus. Cat. No. 352657) measures: 

 Length 4 mm. ; greatest diameter 2.3 mm. 



Not all the specimens assigned to this species show spiral bands, 

 probably due to the thickened porcelainlike layer and enamel. The 

 nearest fossil ally to the new species appears to be Marginella 

 cercadensis Maury, a species occurring in the Cercado formation of 

 the Dominican Republic. The Dominican species, however, has a 

 larger shell and has a much more expanded outer lip. 



Occurence. — Middle or lower Miocene: In flood- wash, Caroni 

 County, Montserrat Ward, 1 mile south of Brasso. 



MARGINELT.A (PERSICULA) PROPEOBESA. new species 



Plate 6, fig. 10 



Shell ovate, rather fragile, posterior extremity well romided, 

 periphery at the posterior third of length, spire about 1 mm. 

 higher than the margin of the outer lip. Spire whorls concealed 

 by caUus; number of whorls indeterminable; body whorl with 

 a callus ridge overrunning the spire and extending parallel with 

 and external to the aperture over the front of the body whorl for 

 half its length; aperture moderately wide, arcuate and slightly 

 expanding anteriorly with a recurved, short, rather wide anterior 

 canal; outer lip arcuate, margin broken away. Columella convex, 

 ornamented with eight plications, the posterior six transverse, equally 

 spaced, gradually enlarging anteriorly and extending posteriorly 

 over one-half the length of the columella, following plication much 

 stronger, slightly biplicate and overruns the pillar externally, an- 

 terior one somewhat smaller, oblique, and marginates the canal. 



Dimensions: Type (U. S. Nat. Mus. Cat. No. 352651) measures: 

 Length 10 mm.; greatest diameter 7 mm. 



The specimens from Montserrat are more mature than the Spring- 

 vale specimen — the outer lip is entire, revealing a moderately strong 

 9116—25 4 



