PLATYCRINID ZA. 651 
clytis HALL = P. scobina Merk and W. 
corrugatus O. and Suum. = P. discoideus O. and Suvm. 
. curryvillensis Row. and Harms =P. equiternus 8. A. MILLER. 
. exsertus Hat = P. burlingtonensis O. and SHUM. 
. Georget Hath = P. Sare Hatt. 
. richfieldensis Hatt and WuitrinLp = P. graphicus H. and W. 
. tnornatus McCu. = P. burlingtonensis O. and Su. 
. lautus 8. A. Minter = P. burlingtonensis O. and Su. 
monroensis WORTHEN = P. Sare Hatt. 
multibrachiatus M. and W.= P. discoideus O. and Su. 
nodobrachiatus Haut 1861 (not 1858) = P. Yuandelli, var. perasper. 
- nodosus WIRTGEN and ZEILER = Culicrocrinus nodosus. 
. nodobrachiatus Hatt 1858 (not 1861) = P. burlingtonensis O. and Su. 
. nodulosus Wan (not Goupr.) = P. ornigranulus McCu. 
- nucleriformis WaLL = P. burlingtonensis O. and Su. 
. olla Hatt 1861 (not DeK. and Lr Hon 1853) = P. Halli Suum. 
. Owent M. and W.= P. regalis Watt. 
P. parvus Wari = Cordylocrinus plumosus (HALL). 
P. penicillus M. and W.= P. Huntsville TRoost. 
P. plano-basalis Rowt. and Harz = P. quinguenodus Warts. 
P, planus Hau (not O. and Su. 1852) = P. Halli Suvum. 
P. plenus M. and W,. = P. Huntsville Troost. 
P. pleuroviminus Wuith = Hucladocrinus pleurovimineus. 
P. plumosus Wart = Cordylocrinus plimosus (HALL). 
P. prematurus HALL = Marsupiocrinus prematurus. 
P. prenuntius W. and Sr. = Hucladocrinus prenuntius. 
P. prattenanus M. and W.= P. Sare Hatt. 
P. pulchellus 8. A. Minter = P. discoideus O. and Sx. 
ramulosus Hat = Cordylocrinus ramulosus. 
. rotundus 8. A. MitieR = P. sculptus Hawt. 
. shumardianus Hatt = P. discoideus O. and Su. 
. striobrachiatus Hatt = P. discoideus O. and Su. 
. sulcatus 8, A. MILLER = P. excavatus Hatt. 
. tenhesseensis ROEMER = Marsupiocrinus tennesseensis. 
. tentaculatus HALL = Marsuprocrinus tentaculatus. 
. truncatus Haut = P. americanus O. and Su. 
. tuberosus Hatt = Hucladocrinus tuberosus. 
Pert wih yyy 
mouth tty thy 
Of the seventeen species in the above list which we have been unable to 
identify, the majority were described either from the basals alone, or these 
with the addition of the radials, and most of them from a single specimen, — 
a practice which cannot be too severely condemned. No paleontologist at 
the present day would undertake to describe an Actinocrinus or Batocrinus 
from a specimen showing nothing but basals and radials; and-why should it 
be done with Platycrinus ? There is often the greatest difficulty in defining 
the limits of species and varieties with an abundance of the best preserved 
specimens in hand. The variation of surface ornamentation in Platycrinus 
is almost without limit. The detached radials and basal plates, beautifully 
preserved and free from matrix, have been collected by thousands from the 
‘soft sandy layers of the Lower Burlington limestone, and it would be possible 
