274 ' NEW UNIONID.E, MELANIDyE, ETC., 



Ova were also found in the ovaries. BrancJike very large and curved below, the 

 inner ones being very much the larger, united the whole length of the abdominal 

 sack. Palpi rather small, thick, rounded below and united only at the upper part. 

 Mantle rather thick, much thickened at the edges, having only a few papillae below 

 the branchial opening. Branchial opening large, brownish, with numerous, regular 

 very small papillte on the inner edges, the papillas in this alcoholic specimen having 

 more the appearance of closely-placed knobs, which decrease in size below. Anal 

 opening very long, without any papillae and entirely disunited from the branchial 

 opening below, while the anal tube and vent nearly protrude beyond the edges of the 

 mantle. Has no super-anal opening. The anterior and posterior adductor muscles 

 are remarkably large, and the abdominal mass is large, compressed and rounded 

 behind. Color of the mass dirty white. 



RemarliS. — Two specimens only were received ; one, a female, in alcohol, from 

 which a careful description of the soft parts is made. Mr. D'Orbigny, in describing 

 his genus Monocondyloea, says the soft parts are the same with the TJnio, but this is 

 not exactly the case. I have seen no TJnio, or other genus of this family, with the 

 same kind of knob-like papillte, nor with an anal opening exactly like that described 

 above. In the outline of the hard parts, or outward covering of this species, it is 

 nearest to Paraguayana, D'Orb., but may be distinguished from it by its darker color 

 of epidermis and its flatness over the umbones, Paraguayana being more inflated 

 there than usual in the genus. Mr. D'Orbigny does not mention that any of the 

 species which he described had undulations of any kind. Nearly all the specimens 

 of the genus which I have seen are eroded at the beaks, except three young ones 

 which I have of two different species, Parchappii, D'Orb,, and Franciscana, Mori. 

 These exhibit no appearance of undulations, while all the numerous species of Unio 

 which I have seen from South America have divergent folds at the tips. The border 

 without pearly nacre is very broad in this species. I have great pleasure in naming 

 this interesting species after Don Patricio Maria Paz y Membiela, Commodore in the 

 Koyal Spanish Navy, who has aided me greatly in developing the South American 

 Unionidce. 



Anodonta Pazii. pi. 3R, fig. 87. 



Testa liBvi, subrotunda, valde inflata, inasquilaterali, postice et antice rotundata ; valvulis crassiusculis ; 

 natibus subprominentibus, acuminatis ; epiderinide tenebroso-rufo-fusca, eradiata, striata ; marga- 

 rita punicea formosissime iridescente. 



Shell smooth, subrotund, very much inflated, inequilateral, rounded before and 

 behind; valves somewhat thick; beaks rather prominent, acuminate; epidermis 

 dark reddish-brown, striate ; nacre deep red and most beautifully iridescent. 

 Proc. Acad. Nat. Sci. 1866, p. 35. 



