26 THE Mr:SOZOIC EICHINODEKMATA of united states, [bcli. 97. 



Tile internodes are traversed by five ligamentous bundles, which are 

 interradially disposed, aud give rise to a more or less petaloid figure 

 ou the joint-faces. No root nor radicular cirri." (P. H. Carpenter.) 



, PENTACRINUS Miller. 

 Pentacrinus asteriscus Meek and Hayden. 



Plate III, Figs. 2a-d. 



Peniacrinus asteriscus Meek and Hayden, 1858. Philadelphia Acad. Nat. Sci. Proc, 



vol. 10, p. 49. 

 Pentacrinus asieriacus Meek and Hayden, 18G0. Philadelphia Acad. Nat. Sci. Proc, 



vol. 12, p. 419. 

 Pentacrinus asteniscus Meek, 1864. Smith. Misc. Coll. (177), p. 27. 

 Peniacrinites asteriscus INIeek aud Hayden, 18G5. Pal. Upper Missouri, Smith. Coutr. 



Knowledge (172), p. 67, PI. in, Fig. 2. 

 '^Peniacrinites asteriscus "Whitfield, 1880. Geol. Black Hills of Dakota, p. 345, PI. in, 



Figs. 1, 2. 



Determinative characters. — Calyx branching. Stem or column com- 

 posed of small, pentagonal joints, rather thick, that bear at intervals 

 small rounded processes or cirri. The column joints are connected by 

 crenated ridges arranged in pentapetalous form. The stem is perfo- 

 rated by a central canal. 



Dimensions. — Column: breadth of joint, 2-0 to y inch; length of joint, 

 3-0 inch. 



Description. — This species was first described by Meek and Hayden in 

 1858, in the Proceedings of the Academy of Natural Sciences of Phila- 

 delphia, from several fragments of the column. The calyx or arms are 

 not known, and, as in the succeeding species, the distinguishing charac- 

 teristics are confined entirely to the column joints. On the large slab 

 figured by Meek and Hayden in the Paleontology of the Upper Mis- 

 souri are several detached portions of the coluuni 1 to 2 inches in 

 length. The sutures are clearly marked and the nodal can be readily 

 sejiarated from the internodal joints. Of the latter, ten are plainly seen 

 between two nodes on one fragment (PI. iii, Fig. 2((), while in other 

 instances the number seems to be slightly greater. All the joints are 

 rather thick (PI. iii, Fig. 2r'). Five cirrus scars are found on each node 

 in the reentering angles. Each node is joined to the underlying inter- 

 node by syzygial suture, while the overlying j)late is connected by 

 crenulated ridges, as are also the internodal plates themselves. The 

 arrangement of these ridges is distinctly petaloid (PI. iii, Fig. 2^). 

 The reentering angles of the outer surface of the stem are not deep, so 

 that the points of each star-shaped prolongation are short and broad. 



The cirri are composed of small round joints that are longer than 

 bVoad. They are joined, as far as could be discerned, by simple sutures 

 (PI. Ill, Fig. 2(7). ^ 



There is some doubt whether the form referred by Whitfield to P. 

 asteriscus in the (ieology of the Black Hills, and so figured and de- 



