314 PROCEEDINGS OF THE ACADEMY OF [1879. 



ihocrinus, except that the arms are recumbent upon the vault. There 

 are five oral plates, upon the sutures between which, and raised, 

 above the general level, the arm-joints are imbedded, being covered 

 by small alternating plates like the free arms. 



Column round, composed of joints of alternating thickness. 



Gissocrinus approaches nearest the Silurian form of Cyatho- 

 crinus ; indeed the form of the catyx and the general aspect are 

 strikingly similar. But they differ in the number of underbasals, 

 which in this genus are reduced to three. Angelin places Gisso- 

 crinus with Forbesiocrinus and both under the Taxocrinidre, which 

 is certainly not a natural group. The long slender proboscis, the 

 single ring of radials within the calyx, show clearly that this genus 

 belongs to the Cyathocrinidse. 



Geological position, etc. Upper Silurian of England and Sweden, 

 so far as known. 



The following species have beeu referred to it : 



1839. Gissocrinus arthriticus Phillips. (Actinocr. arthriticus), Murcbison. Silur. 



Syst., p. 674, pi. 17, fig. 8, and Morris, Cat. Brit. Foss., Ed. 2, 1854, p. 



70. Salter, 1859. Murch. Siluria, Ed. 3, p. 535, pi. 14, fig. 7, and ibid. 



Ed. 4; p. 512 ; Salter, 1873, Cyathocr. arthriticus, Cat. Cainb. and Silur. 



Foss. in Univ. of Cambridge, p. 124. Angelin. Gissocr. arthriticus, 



Iconogr. Crin. Suec, p. 10, pi. 3, figs. 1-3. Upper Silur. Gotland, Sweden, 



and Dudley, Eng. 

 1878. Gissocr. elegans Angelin. Iconogr. Crin. Suec, p. 10, pi. 3, fig. 5. Upper 



Silur. Gotland, Sweden. 

 1878. (?) Gissocr. macrodactylus Angelin. Iconogr. Crin. Suec, p. 10, pi. 18, fig. 



1. Upper Silur. Gotland, Sweden. 



This species differs from all others referred to this genus by 

 Angelin in the brachials, which are represented in a greater num- 

 ber and variable as in Cyathocrinus ; in the branching of the 

 arms, and in having a more elongate calyx. The underbasals are 

 said to be three, but this is not certain. 



1878. Gissocr. nudus Angelin. Iconogr. Crin. Suec, p. 10, pi. 20, fig. 20. Upper 

 Silur. Gotland, Sweden. 



1878. Gissocr. punctuosus Angelin. Iconogr. Crin. Suec, p. 10, pi. 27, figs. 1 a-g ; 

 pi. 29, figs. 73-76. Upper Silur. Gotland, Sweden. 



1878. Gissocr. tubulatus Angelin. Iconogr. Crin. Suec, p. 10, pi. 3, fig. 4. Up- 

 per Silur. Gotland, Sweden. 



1878. Gissocr. umbilicatus Angelin. Iconogr. Crin. Suec, p. 10, pi. 21, figs. 8-10 ; 

 pi. 29, figs. 75 a, b. Upper Silur. Gotland, Sweden. 



