umbilicate

Physarella oblonga B. & C. Sporangium oblong, the apex re-entrant and confluent with the summit of the columella, the base obtuse or slightly umbilicate, stipitate, cernuous.

From The Myxomycetes of the Miami Valley, Ohio by A. P. (Andrew Price) Morgan

Easily recognized by its almost sessile, rose purple, generally umbilicate sporangium.

From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by Thomas H. (Thomas Huston) MacBride

Sometimes they are umbilicate below, so that a vertical section would be obcordate.

From The North American Slime-Moulds A Descriptive List of All Species of Myxomycetes Hitherto Reported from the Continent of North America, with Notes on Some Extra-Limital Species by Thomas H. (Thomas Huston) MacBride

Sporangium depressed-globose, the base umbilicate, stipitate, rarely sessile and plasmodiocarp; the wall a dark-colored membrane with a thin layer of stellate crystals of lime, breaking up gradually and falling away.

From The Myxomycetes of the Miami Valley, Ohio by A. P. (Andrew Price) Morgan

Sporangium large, depressed-globose, the apex umbilicate, stipitate, cernuous, dark purple in color; calyculus usually wholly wanting, the ribs united by weak fibers, which are easily torn asunder, allowing the ribs to curl up inwards.

From The Myxomycetes of the Miami Valley, Ohio by A. P. (Andrew Price) Morgan