18 GEOLOGICAL MEMOIRS. 



On DoRYCRiNus. By Dr. Ferd. Roemer. 



[Wiegm. Arch. 1853, Jahrg. 19. pt. 1. pp. 207-220, with a plate (X.) ; Leonhard 

 u. Bronn's N. Jalirb. f. Min. u. s. w. 1854, p. 253.] 



The Dorycrinus, a new genus of Crinoids, is established by Dr. F. 

 Roemer on specimens from the Carboniferous Limestone of North 

 America, sent with others (of Actinoerinus, Amphoracrinus, Platy- 

 crmus, &c.) to Europe by Dr. Krantz, from the neighbourhood of 

 Warsaw on the Mississippi, in the northern part of the State of 

 Ilhnois. 



The only described species is the D. Mississippiensis (F. Roemer). 



The most striking character of this Crinoid is the presence of six 

 strong tapering processes or spines, sometimes 2\ inches in length, 

 which radiate upwards and outwards from the upper half of the 

 calyx : the latter is about If inch in height. 



The generic characters are as follows : — 



Calyx spheroidal or subcuboidal, perforated by a single excentric 

 lateral opening (mouth), and bearing some long spines on its sur- 

 face. 



Basal pieces three, unequal, forming a flattish disc ; the larger two 

 equal, the suture connecting them leading towards the mouth. 



Radial pieces of first, second, and third order five ; radial pieces of 

 third order axillar, each bearing two distichal pieces of first order, 

 and these again two distichal pieces of second order. The last 

 emarginate on their upper border, and forming, with the next pieces 

 above them, the apertures leading into the calyx for the supply of 

 nutriment to the bases of the arms (lost in the fossil state) . 



Inter-radial piece of first order single, inserted between two radial 

 pieces of first order on that side of the calyx on which the mouth 

 is ; inter-radial pieces of second order seven, three irregularly six- 

 sided placed on the side on which the mouth is, one regularly 

 hexagonal on each of the four remaining sides, placed between the 

 two neighbouring radial pieces of first order. Inter-radial pieces of 

 third order thirteen, five on the side on which the mouth is situated, 

 two on each of the four other sides of the calyx, between two 

 neighbouring radial pieces of third order. 



Top of the calyx : the upper half of the calyx above the places of 

 the arms is composed of numerous pieces. Six larger pieces, five 

 of which are placed above the arms and around the circumference 

 of the top of the calyx, and one at the highest point of the calyx 

 'excentrically and over the mouth, are produced into subulate spines 

 2 inches long. 



Mouth oval, lateral, surrounded with several small pieces, and placed 

 under the isolate spine and between two of the other peripheral 

 spines, which are thicker than the others. 

 Column cylmdrical, articulated, perforated by a cylindrical canal, the 

 surfaces of the joints with fine radial marking. 



The relations of Dorycrinus are best shown in the accompanying 



