PLATYCRINIDAE 63 
area, in contrast to that of 10 arms chiefly characteristic of the American rocks, from which 
it is also sharply distinguished by its elongate, pointed interbrachial jjlate. 
A feature of this species not heretofore mentioned to my knowledge is the tendency to 
grow in clusters, several individuals in a group being attached by their stout stems to corals 
or other fixed objects. I am illustrating this by a slab from Dudley, shown by a reduced 
photograph on plate 19, with nine stems springing from a common base, four of them with 
the crowns attached and visible, and the others with the crowns imbedded in the matrix. 
Such a multiple fixation is unusual among crinoids, but here it seems to be a character more 
than merely incidental, as other specimens are known, one very fine one, for example, in the 
Dudley Museum, and another in the collection of the late Mr. Charles Holcroft, now in the 
Museum of Birmingham. 
Horizon and locality. Wenlockian group, Silurian ; Dudley, England. 
Of other described species there are one by Weller from the Racine dolomite, one by 
Hall from the dolomite at Cedarville, Ohio, one by Hall from the Helderbergian of New 
York ; and four by Angelin from Gotland. 
