6 PROCEEDINGS OF THE NATIONAL MUSEUM vol.69 



terior acluctor scars deep and roii<!:h ; the posterior ones nearly super^ 

 ficial and smooth. Pallial line well marked, about 3 mm. from the 

 ventral margin; prismatic border very narrow. Right valve with 

 a single pseudocardinal tooth, and a single lateral somewhat remote 

 from the beak; left valve with two pseudocardinal teeth, the inner 

 one the larger, and the space between them shallow, broad. Lateral 

 teeth in both valves obliquely striated and grooved. 



The type. Cat. No. 362398, U.S.N.M., measures: Length, 32.5 

 mm.; height, 20 mm.; diameter, 11 mm. It comes from Finca de 

 Providencia, Guatemala, and was received without name from H. 

 Rolle, of Berlin, Germany. 



The nearest ' relative to this species is Quadrula guatemalensis 

 Simpson. The genus Quadrula does not seem to be the proper al- 

 location for guatemalensis nor for the present species, which is here 

 placed doubtfully in the genus EUiptio, to remain until the true 

 generic positions of the Mexican and Central American granulous 

 Maiads are finally determined. 



Cat. No. 362399, U.S.N.M., includes a paratype, in which the 

 granulation is not quite so abundant and on which there are two 

 very broad dark radiating rays which are made up of many very 

 fine greenish radiating lines. It measures : Length, 38 mm. ; height, 

 22.5 mm. ; diameter, 13 mm. 



TETRAPLODON LINKI, new species 



Plate 1, figs. 6, 7 ; plate 3, fig. 2 



Shell subrhomboid, rather thick, subinflated, beaks about the 

 middle of the dorsal line, posterior end obliquely truncate, anterior 

 end narrower and rounded. Posterior dorsal ridge moderately high, 

 subangulate. Hinge line straight, slightly oblique, ventral mar- 

 gin a little arcuate. Sculpture consisting of 28 radiating ribs, 

 which are narrow and subnodulous on the anterior and posterior 

 areas, smooth, wide and low on the middle portion of the shell; 

 concentric sculpture of many raised growth striae which are em- 

 phasized on the radiating ribs; three rest periods indicated. Color 

 uniform ashy olive. Interior pearly, iridescent at posterior por- 

 tion, bluish white, having an appearance of being numerously, finely, 

 radiately striate ; anterior adductor scars deep, posterior scars super- 

 ficial, prismatic border a mere line. Right valve with two pseudo- 

 cardinal teeth, the inner one the larger, and with three small denti- 

 cles behind it on the hinge area ; left valve with one pseudocardinal 

 tooth split into about five denticles. Right valve with one lateral 

 tooth which is short and has many vertical striae on its inner and 

 outer faces; left valve with two lateral teeth, the inner one much 

 the larger and strongly vertically ribbed on its upper face. 



