116 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



joining columns of supramarginal ossicles and about medially be- 

 tween the margin and the center of the disk.]" 



Supplementary description. II unknown, r=7 mm. Width of 

 ray at base 9 mm. 



Abactinal area of rays margined by inframarginals, above and 

 inside of which are columns of large, bipyriform, multispinous, su- 

 pramarginal plates of which there are five in 5 mm. at the base of a 

 ray. The columns of adjoining rays unite in the axillary areas. 

 Inside of the supramarginal columns the rays and disk have numer- 

 ous smaller accessory plates, usually triangular in outline or vari- 

 ously stellate. They lie upon or against each other, each ossicle 

 bearing at least one small spine, and leave between them numerous 

 abactinal openings. Outside of the supramarginal plates in the 

 ambital areas are spicular ambit al plates which cover the abactinal 

 side of the inframarginals. 



Description of the type of Palseaster longibrachiatus. 11 = 38 mm., 

 r = 7 mm., R = 5.4r. Width of ray at base 9 mm. 



Rays large, slender, tapering slowly; actinally somewhat convex 

 at their outer ends, but elsewhere concave. 



Abactinal area unknown. 



Inframarginal plates granular, large, decreasing gradually in size 

 dis tally, highly convex, in outline tetragonal or pentagonal and 

 common to both the abactinal and actinal areas. From 28 to 30 

 plates in a column on each side of a ray. 



Axillary areas occupied by the proximal plates of adjoining infra- 

 marginal columns, and in the interbrachial areas there are two sub- 

 quadrangular or sub triangular interbrachial marginal plates. There 

 may be an additional small single plate in each area. 



Adambulacral plates greatly resembling the inframarginal ossicles. 

 Distally they progressively overlap the inframarginal plates con- 

 siderably, while proximally they gradually increase in size and are 

 entirely inside and depressed beneath the plane of the marginal 

 columns. Orally the columns of adjoining rays unite in two wedge- 

 shaped modified adambulacrals (oral armature pieces) . 



Ambulacral furrows deep and gradually tapering. Ambulacral 

 plates unknown. 



Formation and locality. The type of Palseaster spinulosus (No. 16, 

 Mus. Comp. Zool.) is said to have been found at Cincinnati, Ohio. 

 This is probably an error, since il/s color and preservation indicate 

 the Richmond formation and that it comes from some locality 

 considerably to the north of Cincinnati. The only other known 

 specimen, the type of P. longibrachiatus, was found in the Richmond 

 formation near Clarksville, Ohio, and is in the Harris collection, 

 United States National Museum. 



Remarks. The type-specimen of Palseaster spinulosus, which is 

 free, preserves but the disk and a small proximal portion of the rays. 



