Template:Clark & Twitchell, 1915

• Clark, W.B., Twitchell, M.W. 1915. The Mesozoic and Cenozoic Echinodermata of the United States. Monographs of the United States Geological Survey. 54: 1–341. BHL  
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Nomenclatural acts

New names (76)

• †Amblypygus merrilli Twitchell p. 165
• †Aspidura idahoensis Clark p. 23
• †Astrodapsis arnoldi Twitchell p. 199
• †Breynella gregoryi Twitchell p. 148
• †Cardiaster curtus Clark p. 84
• †Cardiaster smocki Clark p. 84
• †Cassidulus bassleri Twitchell p. 211
• †Cassidulus berryi Twitchell p. 220
• †Cassidulus conoideus Clark p. 80
• †Cassidulus (Pygorhynchus) alabamensis Twitchell p. 172
• †Cassidulus (Pygorhynchus) carolinensis Twitchell p. 146
• †Cassidulus (Pygorhynchus) georgiensis Twitchell p. 170
• †Cassidulus (Rhynchopygus) depressus Twitchell p. 144
• †Cassidulus (Rhynchopygus) holmesi Twitchell p. 140
• †Cassidulus (Rhynchopygus) raveneli Twitchell p. 142
• †Cidaris dilleri Clark p. 23
• †Cidaris georgiana Clark p. 158
• †Cidaris plumasensis Clark p. 31
• †Cidaris pratti Clark p. 114
• †Cidaris shastensis Clark p. 23
• †Cidaris smithi Clark p. 157
• †Cidaris tehamaensis Clark p. 44
• †Coelopleurus aldrichi Clark p. 158
• †Coelopleurus sloani Clark p. 181
• †Cottaldia botula Clark p. 57
• †Dendraster arnoldi Twitchell p. 192
• †Dendraster coalingaensis Twitchell p. 196
• †Diplothecanthus dalli Twitchell p. 218
• †Echinanthus georgiensis Twitchell p. 139
• †Echinobrissus angustatus Clark p. 69
• †Echinocardium depressum Clark p. 214
• †Echinocyamus texanus Twitchell p. 120
• †Echinocyamus vaughani Twitchell p. 160
• †Echinolampas aldrichi Twitchell p. 173
• †Encrinus hyatti Clark p. 22
• †Eupatagus carolinensis Clark p. 153
• †Eupatagus floridanus Clark p. 176
• †Gagaria americana Clark p. 159
• †Hemiaster beecheri Clark p. 96
• †Hemiaster bexari Clark p. 89
• †Hemiaster comanchei Clark p. 90
• †Hemipatagus argutus Clark p. 150
• †Hemipatagus subrostratus Clark p. 151
• †Heterodiadema ornatum Clark p. 56
• †Holectypus cragini Clark p. 34
• †Holectypus pealei Clark p. 33
• †Hypodiadema elegans Clark p. 52
• †Isocrinis californicus Clark p. 21
• †Isocrinis smithi Clark p. 21
• †Laganum archerensis Twitchell p. 161
• †Laganum dalli Twitchell p. 164
• †Laganum eldridgei Twitchell p. 160
• †Laganum floridanum Twitchell p. 163
• †Laganum johnsoni Twitchell p. 162
• †Leptarbacia Clark p. 53
• †Leptarbacia argutus Clark p. 53
• †Linthia alabamensis Clark p. 153
• †Linthia wilmingtonensis Clark p. 152
• †Macropneustes carolinensis Clark p. 154
• †Micropsis lineatus Clark p. 63
• †Oligopygus floridanus Twitchell p. 169
• †Ophioglypha utahensis Clark p. 29
• †Orthechinus pretiosus Clark p. 118
• †Orthopsis planulata Clark p. 54
• †Pentacrinus shastensis Clark p. 28
• †Pentacrinus tehamaensis Clark p. 35
• †Periarchus protuberans Twitchell p. 133
• †Sarsella gregoryi Clark p. 155
• †Schizaster americana Clark p. 176
• †Schizaster armiger Clark p. 152
• †Schizaster floridanus Clark p. 175
• †Scutella andersoni Twitchell p. 183
• †Scutella mississippiensis Twitchell p. 124
• †Scutella tuomeyi Twitchell p. 125
• †Sismondia arnoldi Twitchell p. 182
• †Sismondia coalingaensis Twitchell p. 183