1458 MYCi:TOPon.\ 



arated from the nearly smooth anal opening by a strong 

 bridge ; superanal opening not closed below : foot very long, 

 developed at the lower end into a sort of head or button. 



'I'ype, Mycctopoda soleniforntis d'Orbigny. 



So named by its author in the Guerin Magazine, but after- 

 wards changed by him to Mycclo/^us in the \'oyage Amerique 

 Meridionale. The genus has been made the type of a separate 

 family by Gray, and was so acknowledged by Gill, Pelseneer 

 and others, but it does not seem to me to be separable from 

 the Mutelidce. 



The genus Mycetopoda is a well-characterized group con- 

 taining a few South American forms, all of which have elon- 

 gated, delicate shells and a foot capable of great extension 

 and are. no doubt, without exception, burrowers. Although 

 the shells of Solenaia closely resemble those of this group and 

 the species of that genus undoubtedly burrow, I have every 

 reason to doubt that there is any close relationship between 

 them. The shells of Solcnaia are of different texture and they 

 show a ruder growth than do those of Mycetopoda. Such 

 vestigial teeth as the former have are distinctly schizodont, 

 while those of Mycetopoda, when at all developed, are taxo- 

 dont. 



I do not feel at all sure that the different so-called species 

 sil'iquosa, occidentalis, staiidifti^cn, subsinuata, pygmcca and 

 hupeana are anything more than variations of one widespread, 

 abundant and variable form. T have material before me. 

 which differs somewhat from any of the above, but I do not 

 feel justified in bestowing on it either specific or varietal 

 names. 



Group of Mycctopoda siliquosa. 



P)eaks in front of the center of the shell : anterior end evenly 

 rounded; basal lines nearly straight; posterior ridge (|uite low.. 

 Animal with the characters of the genus. 



Mycctopoda sii,iotu)sa (Spix). 



Shell somewhat elongated, thin, inecjuilateral, scarcely in- 

 flated, ga]iing at the anterior base, subtrapezoid ; beaks but 

 moderately full : posterior ridge well-developed, usually rather 



