ART. 2 NEW MOLLUSKS FROM SOUTH AMERICA MARSHALL 5 



obscurely banded with chestnut. At the rest periods the bands 

 become prominent and very dark. Interior rosy with the dark 

 bands of the exterior showing lavender tints, the columella ochra- 

 ceous buff, outer lip the same color with the dark banding much 

 emphasized at the margin. 



The type (Cat. No. 380696, U.S.N.M.) measures: Height, 65 mm.; 

 diameter, 52 mm.; length of aperture, 45 mm.; width of aperture, 

 SO mm. 



It and three paratypes (Cat. No. 380697, U.S.N.M.) and a lot of 

 embryonic shells (Cat. No. 380698, U.S.N.M.) come from a small 

 stream in a dense jungle, 13 kilometers south of Puerto Santos, 

 Province of Santander del Norte, Republic of Colombia, and were 

 collected and presented by Dr. R. H. Palmer. 



The fine coloring, the slightly elongated form, and especially the 

 microscopic sculpture of this species will serve to distinguish it. 



DIPLODON YAGUAEONIS. new species 



Plate 2, Figures 2, 3, 5, 6 



Shell elongate, nearly subelliptic, rather thin, rounded in front, 

 obliquely subtruncate and roundly pointed at the rear. Beaks set 

 about 13 mm. behind the extreme front end of the shell and 50 mm. 

 in front of the extreme back end. Beaks sculptured with strong 

 radiating ribs. (This sculpture is better shown in the three para- 

 types. It consists of about 20 ribs, covering practically all the young 

 shell, the central pair joining to form a long V and continuing then 

 for some distance as a single rib). Dorsal margin lightly arcuate, 

 fading into both the anterior and posterior margins. Ventral 

 margin very slightly curved, nearly straight, rounding into the 

 anterior margin and making a rounded point with the posterior 

 margin. Posterior ridge rather high, rounded. Anterior ridge not 

 differentiated from the general surface, the descent to the anterior 

 margin steep. Concentric sculpture as shown with a lens, of very 

 fine growth striae, the rest periods plainly indicated by a slight 

 elevating of the older portion of the shell above the newer portion, 

 and accentuated by a deepening of color; lamellose on the anterior 

 and posterior areas and as the ventral margin is approached. Color 

 uniform dark chestnut, slightly glossy on middle portion. Interior 

 of a bluish cast, iridescent, appearing to be radiately striated, the 

 rest periods plainly showing as concentric ridges and perceptible to 

 the touch. Anterior adductor scar deep; the posterior one super- 

 ficial. Pallial line well marked at the front, obscure at the rear, 

 set about 4 mm. from the ventral margin. Pseudocardinal tooth of 

 left valve thin, tongue-shaped, fitting into the narrow groove formed 



