25 



In that species the hinge has only a single tooth, stouter or with an 

 obsolete one at its base. 



TELLINA TERSA (PL XVI. Fig. 2.) 



T. modica, convexiuscula, ovato-triangularis, alba, concentrice vix striata : 

 apice postmediano ; latere antico rotundato, superne comprcsso; latere postico 

 triangular!, apice subacuto. margine dorsali recto, cito desinente : dentibus late- 

 ralibus obsoletis. 



Shell moderately large, inequilateral, rather convex, ovate-trian- 

 gular, white, varied with milky and watery white zones ; incre- 

 mental striae fine and irregular ; apex one fifth nearest the poste- 

 rior end, which is triangular, (the dorsal slope very rapidly 

 declining,) slightly truncate at tip, the submarginal flexure well 

 marked ; anterior half broadly rounded, dorsal edge somewhat 

 compressed ; ventral margin regularly arcuate ; lateral teeth want- 

 ing, or consisting of a slight submarginal ridge. 



Diameters, longitudinal one inch ; vertical seven tenths of an 

 inch ; transverse three tenths of an inch. 



Inhabits Panama. Col. Jewett. 



It has a general resemblance to T. Uneata, Turt., but is smaller, 

 thinner, more compressed, and has no lateral teeth. It is more 

 closely allied to T. plebeja, but is more equilateral and quite white. 

 It has so few obvious characters that it is very difficult to describe. 



TELLIXA PURA (PI. XVI. Fig. 3.) 



T. parva, sub-elliptica, vix ineqnilateralis, tenuis, lucida, vel zonis lacteis 

 zonata. striis minutissimis radiata ; apice acuto ; latere antico semi-ovali ; latere 

 postico modice angustato, truncate, hiante, plica admodum conspicua: intus 

 uitida, striis elevatis tenuibus radiata ; dentibus lateralibus carentibus. 



Shell small, compressed, suboval, nearly equilateral, thin and 

 lucid except where obscured by zones of opaque white, shining, 

 with numerous microscopic radiating striae; apex acutely elevated ; 

 anterior half semi-elliptical, rounded at extremity; posterior half a 

 little narrowed, the dorsal margin declining in nearly a right line, 

 tip moderately truncate. Within, shining, and marked by nume- 

 rous minute, raised, radiating lines ; lateral teeth wanting. 



Diameters, longitudinal, one inch ; vertical three fifths of an 

 inch ; transverse three tenths of an inch. 

 4 



