1881.] NATURAL SCIENCES OF PHILADELPHIA. 2^5 



Basals three, unequal ; two of them pentagonal, the third 

 smaller bj' one-half, and quadrangular. Primary radials 3X5; 

 the first ones forming laterally a continuous ring, larger than 

 those succeeding, heptagon'al, the lateral margins very long ; the 

 second quadrangular, wider than high ; the third axillary of 

 medium size, ui)per angle obtuse. Secondary radials 2 X 10, 

 which directly support the arms, or sometimes the second plate 

 is the bifurcating piece, and supports upon the inner and wider 

 sloping side an arm ; upon the smaller side an extraordinary large 

 pinnule, which takes the direction of the arm, being more erect 

 than the succeeding pinnules, and twice as heavy. The arms are 

 large, heav}' at the base, and towards the tips gradually tapering 

 hito a sharp point. The proximal arm plates are large, resembling 

 secondary radials, and like them are decreasing in height up- 

 ward ; succeeding joints cuneate, gradually passing into two 

 rows of interlocking pieces. In P. pinnulatus they pass scarcely 

 beyond the earliest stage of interlocking arms ; in P. chiastodac- 

 tylus the arms remain single-jointed throughout, but the joints 

 are strongly cuneiform. Pinnules long, rather strong, and com- 

 posed of single joints. 



Interradials three, the first very large, with a small one in the 

 second, and a still smaller triangular one in the third series, the 

 latter abutting against the large proximal arm-like pinnules. 

 There ai'e some species with five interradials, having two plates in 

 the second, and two in the third range. Anal side not structurally 

 distinct. 



Yault unknown, anal aperture apparently lateral. 



Column cylindrical. 



This genus, in its general habitus, resembles Agaricocrinus, 

 particularly its earlier and smaller species ; but the two genera are 

 very distinct in the construction of the anal area. 



Geological Position, etc. — Patelliocrinus, so far as now known, 

 is confined to the Upper Silurian of Europe. 



We recognize the following species : — 



1S7S. Patelliocrinus chiastodactylus Angelin. Icongr. Grin. Suec, p. 1, PI. 19, 



fig. 12. Upper Silur. Gvjthland, Swede n. 

 1878. Patelliocr. interradius Angelin. Iconogr. Grin. Suec, p. 2, PI. 22, fig. 10. 



Upper Sihir. Gothland, Sweden. 

 1878. Patelliocr. leptodactylus Angelin. Iconogr. Grin. Suec., p. 2, PI. 16, figs. 26, 



31. Upper Silur. Gothland, Sweden. 



