REWSTON OF PALEOZOIC STELLEROIDEA. 83 



Inside the ring the pLitcs can not be made out, (hie to the small size 

 of the specmien. Rays each with a oohimn of rathals and tv/o supra- 

 marginals between which are inserted cohimns of (hagonally arranged 

 accessory plates. A few ambital accessory plates are probably also 

 present. The arrangement of the ossicles on the abactinal areas of 

 the rays is like that in Promopalseaster magniflcus. 



Madreporite small, subconical, situated near the edge of the disk, 

 depressed between adjoining basal plates and marked by 10 or 11 

 sharp, somewhat spirally arranged ridges. 



Inframarginal plates large, about six in each column proximal to 

 the very large single axillary interbrachial plate. These columns in 

 the distal half can not be seen actinaUy as they pass over on the dorsal 

 side. 



Axillary interbrachial plates large, one m each axil, and not com- 

 pletely inclosed outwardly by the basal inframarginals. In this 

 character the form is still in the Iludsonaster stage. 



Adambulacral plates small, subquadrangular, wdth 16 plates in each 

 column. The plates of the adambulacral oral armature are larger 

 and wedge-shaped, and are situated directly inside of the axillary 

 interbrachial plates. 



Ambulacral plates one to each adambulacral, apparently opposite 

 and with proxunally converging I'idges. Podial openings apparently 

 along the outer edge between the sutures of adjoining plates. 



Formation and locality. — Two specimens were found by the late 

 Prof. Charles E. Beecher near Rome, New York, in the Triarthrus 

 bed of the Utica formation that preserves the entu-e ventral anatomy 

 of these trilobites. The cotypes are in the Museum of Yale University. 

 Mr. W. S. Valiant in a letter states that they are common in a layer 

 2 to 3 inches above the Triarthrus bed. 



RemarJcs. — This species is most closely related to M. Jinei, from 

 which it is readily distinguished abactinaUy. Here there are more 

 and smaller plates than in 21. lanceolatus, the interpolated plates are 

 arranged diagonally and not radially as in M. jinei, while the basal 

 plates of the former are apparently much larger and are strongly stel- 

 late. ActinaUy there are in M. lanceolatus more adambulacral plates 

 in each column, although the specimens arc only haK the size of M. 

 jinei. 



MESOPALjEASTER PROAVITUS, new species. 



R=18 mm., r^about 4.5 mm. The specimens are distorted, however, 

 and no exact measurements can be given. 



On the distal abactinal portion of the rays the infra- and supra- 

 marginal and radial plates closely adjoin. ProximaUy, however, 

 between the two marginal series there is inserted a column of inter- 

 calary plates gradually increasing in size and two other similar rows 

 of plates are placed between the supramarginal and radial columns. 



