MYCKTOrODA I 46 1 



dorsal area are two or three broad, radiating ridges. The 

 specimen from Piricacaba is only y^^ "i"!- long and yet. accord- 

 ing to the muscular impressions, fully grown. Connpared with 

 it, M. orhignyi reaches double the size, even to 140 mm. in 

 length. According to d'Orbigny, this species lives both in 

 Bolivia and the Rio de la Plata." (von Ihering). 

 Mycetopoda siliquosiis d'ORBiGNY, Guer. Mag., 1835, P- 4^- 

 Mycetopus siliquosus d'ORciCNY, Voy. Am. Mer. Moll., 1843,. 



p. 601, pi. 1.XVI1. 

 Mycetopoda siliquosa. (part), Simpson, Syn.. 1900, p. 934. 

 Mycetopoda orhignyi vox Ihering, Abh. Senckenb. Ges.,. 



XXXII, 1910, p. 121. 



Mycetopoda occidrnt.m.ts Clessin. 



Shell somewhat elongate, subtrapezoid, subinflated, thin, 

 shining, brownish-green : beaks rather full ; dorsal line straight 

 behind the beaks, incurved in front of them ; anterior end nar- 

 rowed, rounded, subangulate above ; base line curved a little ; 

 posterior end wide, rounded, subangulate above and below; 

 nacre bluish-white. 



Length 06. height 44, diam. 2T, mm. 



Rio Patasa,. Ecuador. 

 Mycetopoda occidentalis Clessin. Mai. I. Bl. i, 1879, p. 174^ 



pi. XI, figs. 2, 3. — Simpson, Syn., 1900, p. 934. 



This species has a somewhat trapezoid shell and is unusually 

 high in proportion to its length. The anterior end is consid- 

 erably narrowed ; the posterior end is wide, and though al- 

 most evenly rounded is bluntly angled above and below, a 

 character not found in any other species that I know of. 



Mycetopoda subsinuata (Sowerbv). 



Shell elongated, irregularly obovate, inflated, thin, gaping 

 in front, inequilateral ; beaks only moderately elevated ; hinge 

 line straight behind the beaks, slightly incurved in front of 

 them ; anterior end evenly rounded, narrowed ; base full at 

 and behind the middle, subsinuate anteriorly ; posterior end 



