22 



Family MITROCRINIOE, n. fam. 



MiTitocKiNUS, n. gen. 



[Ety mitra a turban; krinon lily.] 

 Calyx depressed; vault elevated. Basals three, equal. Primary 

 radials three by six. Secondary radials. No subradials. Regular 

 interradials three. Azygous interradials three or more, the first 

 one resting on a single basal. 



The peculiarities in this genus are the six radial series instead 

 of five, and the resting of the first azygous plate on a single basal 

 instead of on two basals. Beside this genus is from the Trenton 

 Group and is the only one having three equal basals, thus far 

 known, from the Trenton rocks of America. Type M. Weih- 

 erbyi. 



This genus cannot be referred to any of the described families, 

 if any regard is paid to the structure of the calices. The speci- 

 men is quite complete, on which the genus is established. It is 

 symmetrical in all its parts, and a line drawn through the center 

 of the azygous area will cut it in two equal parts, leaving three 

 radial series upon each. The three basal plates are almost abso- 

 lutely equal, notwithstanding one of them supports an azygous 

 plate. The vault is as perfect as that of any other crinoid and 

 has a resemblance to that of a Dorycrinus. Under the circum- 

 stances we propose the new family name Mitrocrinidce and ascribe 

 to it the following characters: Basals three. Primary radials 

 three by six. No subradials. Regular interradials. Whether 

 other characters ascribed to the genus will be found to be of fam- 

 ily value will depend upon future discovery of allied genera. 



MITKOCRINUS WETHERBYI, n. Sp. 



Plate II, Fig. If, azygous view, the central spine may be seen be- 

 yond the azygous opening and two of the subspinous 

 plates on the sides, but the plates of the azygous side 

 are small and sutures too obscure for correct 

 illustration; Fig. 5, basal view, azy- 

 gous side above; Fig. 6, Sum- 

 mit view. 



Calyx depressed, radial elevations distinct, but not specialized as 

 ridges; interradial areas concave; sutures slightly beveled; surface 

 granular; height less than half that of the vault; arm openings 

 directed horizontally. 



