478 MEMOIRS OF THE CARNEGIE MUSEUM. 



3. DiPLODON HASEMANi Ortmaiiii, 8p. nov. 



PI. XXXIV, figs. 1 to 4, shells; PI. XLVII, fig. 5, section of gills; text-fig. 4a (p. 



469), glochidium. 



Locality. — Rio Giiapore, near Rio Sao Simao, Matto Grosso, Brazil (John D. 

 Haseman coll., July 20, 1909). Nineteen specimens investigated, all with soft 

 parts; sex of the three smallest not ascertained; the rest were males and gravid 

 females. 



Type-set: Cam. Mus. No. G1.5857, twelve specimens, among them four males 

 and five gravid females, one with eggs, the others with glochidia. 



Description of SkelL — Shell small (max. length 28 mm.), solid, swollen, short, 

 subovate, somewhat pointed behind. Diameter G7 to 72 pr. ct. of length, as against 

 59 to 68 pr. ct. in D. guaranianus. Valves not gaping. Dorsal margin gently 

 convex, passing gradually or with a blunt angle into the anterior margin, which 

 is sometimes almost truncated. The posterior upper margin forms an obtuse, 

 rounded angle with the posterior margin, the latter descending obliquely, gently 

 convex, forming with the lower margin a rather distinct, but blunt posterior ter- 

 mination of the shell, which is little elevated above the base-line. Lower margin 

 gently and uniformly convex, passing in a regular curve into the anterior margin. 

 The anterior i^ortion of the shell does not appear appreciably narrower than the 

 posterior, or very little so. 



Valves convex, more so in older specimens, with a rather distinct, but rounded 

 umbonal ridge. Posterior sloi)e subtruncated, a little compressed and elevated 

 in the middle. Greatest diameter of shell 42 to 55 pr. ct. of length (32 to 52 pr. ct. 

 in D. guaranianus). This greatest diameter located more forward toward the 

 beaks than in D. guaranianus. Beaks somewhat swollen, but little elevated above 

 the hinge-line, located at 25 to 28 pr. ct. of the length. Beak-sculpture of the 

 hylams-type, strongly developed, the posterior bars thicker and longer than the 

 anterior. Thej^ cover 10 to 15 mm. of the shell, that is to say, hardly half of it 

 in larger specimens. There arc from fourteen to sixteen of them, and the ninth 

 and tenth generally meet at an acute angle, with sometimes a short odd one between 

 this pair. The anterior bars are sharp, the posterior ones broader and rounded, 

 but not so much as in D. guaraniamis. There are often three or foiu' additional 

 finer bars upon the posterior slope, and some oblique wrinkles behind and below 

 them. The lower ends of the bars are but faintly cut up into tubercles. A lanceo- 

 late, rather short, lunula may be present in the larger specimens. 



Epidermis with numerous, concentric, irregular striae, finely lamellar in young 



