56 



MYCETOPUS. 



Ill SUBGENUS MYCETOPUS. 



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WIDE. 



soleniformis. D' Orb. 

 Spatha soleniformis. 



*siliquosus. JD' Orb. 



An. siliquosus. Spix 



Ant. Kilst. 



Kilst. 



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^tn. pygmoeum (junior). 

 An. longinus. Spix. 

 Irid. longina. Fer. 



ventricosus. 2 D' Orb. 



Sp 



1 This genus, established by M. D'Orbigny, has the dorsal margin smooth like Anodonta; but that and the 

 basal margin are nearly parallel, and the posterior margin is truncate. The soft parts of the animal figured by 

 D'Orbigny represent it to be very different in the form and size of the foot, which it extends enormously. He 

 mentions that the two anterior cicatrices are widely separated. A more important character appears to be in the 

 fact that the smaller cicatrix is placed before the larger one. In the Uni.o and Anodonta, it is placed below it, and 

 in the Syria, Lam., it is placed above, that is, in a line with the beak. Its habits are different from the Unionidee 

 generally, as it buries itself over a foot in the sand, "perforat, sicutpholadse." In this characteristic it is analogous 

 to Margaritana dehiscens (p. 43), Unio dehiscens, Say, which my brother, T. G. Lea, informed me he found only 

 at a depth of 12 inches below the surface of the sand on the bars of the Eiver Ohio, their position being ascertained 

 by a small hole at the surface kept open by the animal. I have never seen the soft parts myself, but I presume the 

 animal does not possess a very extensile foot, and yet it may have power to extend some portion of its body into 

 this hole. 



3 Voyage dans VAmirique Miridionale, torn. v. partie iii. PI. 72, Fig. 1 — 3. The figure of ventricosus ap- 

 proaches so much that of siliquosus, that I would not be surprised if it should prove to be simply a variety. 



