ART. 22 MIOCENE GASTROPODS AND SCAPHOPODS MANSFIELD 47 



of faint axials and on the following whorls of (fifteen to seventeen 

 on the penultimate whorl) moderately strong, slightly protracted 

 ribs extending across the spire whorls and to the basal shoulder on 

 the body whorl. Spiral sculpture of equal strength to axial and 

 consists of slightly rounded, narrow cords, four to five in number 

 on the spire whorls and fifteen on the body whorl and canal, being 

 weakly nodulous at the intersection witli the ribs. Outer lip broken 

 away. Inner lip apparently bearing a callus. Columella medialh* 

 enlarged, tapering below and bearing oblique cords. 



Dimensions: Cotypes (U. S. Nat. Museum Cat. No. 352672) meas- 

 ures: Specimen A (with better preserved upper whorls), altitude 16.5 

 mm. ; greatest diameter 6 mm* Specimen B, altitude 14.5 mm. ; great- 

 est diameter 6 mm. ; length of aperture 6 mm. 



The description and figures of Stromhina costaricensis Olsson 

 from the Gatun formation. Headwater of Middle Creek, Costa Eica, 

 appear to match closely the Trinidad form. However, the diameter 

 of Olsson's species is proportionately greater and the spirals 

 weaker. 



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

 County, Montserrat Ward, 1 mile south of Brasso. 



Genus STROMBINA Morch 



STROMBINA WALLI, new species 



Plate 8, figs. 5, 7 



Shell small, solid, with a moderately short spire and a broad body 

 whorl, eight whorled. Nucleus large, smooth, broadly conical, 

 whorls convex and weakly constricted at the suture. Following 

 whorls tabulated below the suture, spire whorls nearly straight in 

 outline. Axial sculpture only on the three postnuclear spire whorls 

 of (about twelve on the penultimate whorl) indistinct, rather broad 

 axials, being more prominent at the base of the whorl. On some 

 specimens, the axials are almost indiscernible. Last whorl smooth 

 and flattened dorsally between a broadly rounded ridge on the left 

 side and the very large outer lip. Aperture narrowly ovate, deeply 

 incised behind with a short reflected anterior canal. Outer lip heavy, 

 depressed behind the margin of facial surface and provided with 

 seven denticles within; upper ones strong, lower ones very weak. 

 Inner lip heavily calloused and provided with four denticles along 

 the columellar border. Base of body whorl and columella spirally 

 sculptured with about twelve cords. 



Dimensions: Type (U. S. Nat. Mus. Cat. No. 352671) measures: 

 Altitude 6 mm. ; greatest diameter 3.4 mm. ; length of spire 2.2 mm. ; 

 length of aperture 3 mm. A larger specimen with a missing outer lip 



