90 



MYCETOPUS. 



III. SUBGENUS MYCETOPUS. 1 



to 



$5 



i 



WIDE. 



plicatus. 2 Gray. Reeve. 



WIDE. 



soleniformis. D'Orb. Chenu. Han. 

 Spatha soleniformis. Ant. Kilst. 

 Myc. pygmseus. Hupe. 

 Myc. Weddellii. Hupe. 



*emarginatus. s Lea. Sow. Reeve. 

 *falcatus. 4 Higg. & Reeve, No. 9. 



g 



M 



5. 



WIDE. 



*siliquosus. D'Orl. Han. 



An. siliquosus. Spix. Kilst. More. 

 An. lonyinus. Spix. 

 Myc. subsinuatus. Sow. Reeve. 

 Irid. longina. Fer. 

 Lamproscapha siliquosa. Swain. 



*pygmaeus. ! Spix. 

 rugatus. Sow. Reeve. 

 ventricosus." D ' Orl. 



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 TJnio and Anodonta, it is placed below it, and in Hyria, Lam., it is placed above, that is, in a 

 line with the beak. Its habits are different from the Unionidse generally, as it buries itself over a foot 

 in the sand, "perforat, sicut pholada?." In this characteristic it is analogous to Margaritana dehiscens 

 (p. 69), Unio dehiscens, Say, which my brother, T. Gr. Lea, informed me he found only at a depth of 12 

 inches below the surface of the sand on the bars of the River Ohio, their position being ascertained by 

 a small hole at the surface kept open by the animal. The foot is capable of great extension. See 

 description of soft parts, Obs. Vol. X. p. 76. 



1 This has very much the appearance of a deformed shell, as figured by Reeve, No. 3. 



8 Mr. Conrad proposes to create a new genus (Solenaia) for this species (Am. Jl. Conch., vol. iv. p. 

 249), it having, he says, "a lateral tooth in each valve," which it has not, there being then only a "slight 

 long rising," as originally described by me. I presume Mr. Conrad had never seen the shell. 



4 Mr. Higgins has described and figured this species (Zool. Pro., 1868, p. 179), which he received from 

 Mr. E. Bartlett, who discovered it in streams near Chyaretas, Upper Amazon. It is closely allied in 

 all its characters to emarginatus (nobis), and I have admitted it above as a distinct species. If the 

 habitats be correct, and I have no reason to doubt them, we have in Mr. Wheatley's collection and 

 mine, together with Mr. Higgins' authority, the two distant habitats well established. Falcatus seems to 

 be a smaller species, more emarginate, corrugate on the posterior slope, and the angles of umbonial and 

 anterior slopes are more acute. 



6 Having the two shells An. siliquosa and An. pygmsea, Spix., before me, I cannot doubt of their 

 being distinct; and I believe they both belong to D'Orbigny's genus Mycetopus. 



6 Voyage dans VAmerique Meridionale, torn. v. partie iii. PI. 72, Fig. 1-3. The figure of ventricosus 

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



