CRINOIDS AND BLASTOIDS. 169 



to the third radials ; the succeeding ones comparatively smaller. 

 Azygous interradius unknown and likewise the ventral cov- 

 ering. 



The surface ornamentation of this species is different from 

 that of any other with which we are acquainted. The surface 

 of the plates is indented with numerous shallow polygonal pits 

 and short grooves, whose rims, which are somewhat rounded 

 off, connect with one another from plate to plate, and on the 

 same plate, in intersecting wrinkles. There is no very definite 

 arrangement of either pits or wrinkles, but the whole surface 

 has a somewhat irregular cancellate sculpturing, not unlike the 

 appearance of the parasitic Chastetes. 



Column round, composed of very short joints of nearly uni- 

 form diameter so far as we have observed them, and alternat- 

 ing in thickness. 



Geological position, etc.: Same as last. 

 Collection of Hon. Delos Arnold. 



GENUS MEGISTOCRINUS Owen & Shum. 

 MEGISTOCRINUS NOBILJS (nov. sp.) W. & Sp. 



PI. XVI, Fig. 6. A large specimen with arms. 

 P . XVI, Fig. 7. Another specimen. Ventral view. 



Calyx large, broadly urnshaped, truncate at the bottom, with 

 deep constrictions or depressed areas at the brachial zone 

 between the rays and their divisions. Vault usually but little 

 convex, forming almost a plane, except along the azygous side, 

 which is more or less depressed, while the plates surrounding 

 the anal aperture are slightly elevated. The specimens are of a 

 light grey, intermediate between the lightest and darkest fossils 

 of this locality. 



Basals comparatively small, resting within a shallow cavity, 

 produced by the bending in of the lower portions of the first 

 radials. They form a very regularly hexagonal disk, with a 

 conspicuous rim enclosing the upper stem joint. The plates are 

 closely anchylosed, and the interbasal suture but indistinctly 

 visible, while the basi-radial sutures are deeply beveled. 



