98 PROCEEDINGS OF THE ACADEMY OF [1886. 



open in all onr specimens, but probably was covered in a similar 

 manner as in Si/mbathocrinus. 



The arniJ^ are long, simple, rounded along the outer face, and 

 less closely fokled than in SinnbotJiocrinus. They are composed 

 of extremely long, single joints with parallel upper and lower 

 faces. The column is circular and has a stellate central canal. 



Geological Positioyi, etc. Pisoci-imis is restricted to the Upper 

 Silurian, and occurs in Europe and America. 



Pisoci'inus Dixoni Troost is a catalogue name. 



1S78. Pisoorinus flagellifer Angclin, loonogr. Crin. Suec, p. 21, PI. 4, figs. 1 a-e. 



Upper Silur., Gothland, Sweden. 

 1S7P. P. gemmiformis ?. A. Miller. Journ. Cincin. Soc. Nat. Hist. (,July), PI. 9, 



lii;s. (i (!-<-. Niagara gr.. Kiply Co., Indiana. 

 1S7S, P. oUula Angelin, Iconogr. Crin. Suec., p. 21, PI. 4, figs. 4 a-rf. Upper Silu- 

 rian, llothland, Sweden. 

 ISoS. P. ornatus I>e Konim-k. Hull, de TAcad. Roy. de Bolg. (Ser. 2), Tome 4 (Extr. 



p. 27), PI. 2, figs. 12, 13. Upper Silurian, Dudley, England. 

 ISoS. P. pilula De Koninek (Type of the genus). Bull, de I'Aoad. Koy. de Belg. 



^Ser. 2), Tome 4 (Extr. p. 2ti), p. lOt^, figs. S-11 : Angelin, lS7v^, loonogr. 



Crin. Suec.. p. 21, PI. 4, figs. 4 <i, ft. Upper Silurian, Dudley, England, 



and l<othland, Sweden. 

 1S7S. P. pooillum Angelin, loonogr. Crin. Sueo., p. 21, PI. 4, figs. :i, ."^ <i. Upper 



Silurian, Gothland, Sweden. 

 *lSiUi. P. tenuesseensis (Koouier). Symbathoorinus tennesseensis. Silur. Fauna, 



West. reuu.,p. .'>'>, PI. 4, figs. t> o. />. Niagara gr. Dooatur Co., Teun. 



TRIACRINUS Miinster. 



ISr^O. 3Tunstor, Boitnige ?.. Potrefiu-tonk., p. 8. 

 1S50. D'Orbigny, Prodr. do Valeont., i, p. 104. 

 1866. Schnltze, Monogr. Eehin. Eifel Kalk., p. 106. 

 1879. Zittol, llaudb. d. Pahvont., i, p. 348. 



Syn. 2'richocnnus Miillor. ^Monatsbor. ISoO. p. 3o4., and Xouo Ecbin. 

 d. Eitl. Kalk., p. 04?. 



Triacrinus ditVer^s from Pisocrinus in having three basals in 

 place of five, in all other eharaoters the two forms are identical. 

 "We have some doubt whether the few species which have been 

 referred to TriacHnus have not really five basals instead of 

 three. In this case the genus would take the name Pisocrinus 

 and not 'Triacnnus, although the latter has priority. Miinster 

 described the base as tripartite, making this the name-giving 

 character, and Pe Koninok, who found five basals in his species, 



