@misc{indiciae3b21c5c72698,
  title = {The Mesozoic and Cenozoic Echinodermata of the United States},
  author = {William Bullock Clark and Mayville William Twitchell},
  year = {1915},
  doi = {10.3133/m54},
  url = {https://pubs.usgs.gov/publication/m54},
  note = {Source identifier: m54}
}