604 



MEMOIRS OF THE CARNEGIE MUSEUM. 



the anterior i)osition of the beaks, the sub-pointed posterior end, and the radial 

 rib upon the posterior slope. Tlio dark green color of the disk may also be charac- 

 teristic, but this is liable to fade; in our specimen from Asuncion, a much-worn 

 shell, the remnants of the epidermis are brown. 



Measurements. 



Anntomy. — The soft parts of a young male and a gravid female (collected 

 June 12) are at hand for study. 



The typical AnodoiUites-structure is observed. The mantle-connection separat- 

 ing anal and branchial openings is rather long. The branchial opening has ex- 

 tremely fine papillse. The inner edge of anal and branchial is brown. Palpi of 

 medium size, semicircular, with a short posterior truncation. 



In the gravid female the eggs fill the water-tubes of the inner gill, with ex- 

 ception of those near the extreme anterior and posterior ends. Tlie water-tubes 

 are markedly expanded, and the eggs are located in the basal part of the tubes, 

 and only in the inner compartment (ovisac) toward the inner lamina of the gill. 

 No larvae were seen. The outer gills have the usual structure of alternately thicker 

 and thinner septa, while the septa of the inner gill are more uniform and thicker. 

 The gills of my female are much torn and injured, so that it was not expedient to 

 section them. 



54. Anodontites hyrioides Ortmann, sp. nov. 

 Shells: Plate XLII, figs. 3, 4, 5. 



Type-locality. — Rio Tapajos, Santarem, Para, Brazil (J. D. Haseman coll., 

 December 6-12, 1909). Type-set: Carn. Mus. Cat. No. 61.5829. Six specimens. 



Characters of the Shell. — Shell moderately thick, angularly subovate, some- 

 what oblique, pointed behind, lower margin convex, forming a blunt angle. Height 

 62 to 73 pr. ct. of the length. Valves not gaping. Dorsal margin practically 

 straight, gently descending in front of the beaks. Posterior angle of dorsal margin 

 obtuse, but quite distinct, wing-like. Anteriorly the dorsal margin forms also a 

 more or less distinct angle, which is obtuse or almost a right angle. Posterior 

 margin obliquely descending, straight, or slightly concave in its upper portion, 



