KEVISION OF PALEOZOIC STELLEEOIDEA. 63 



by its author, and it is like other specimens in the Harris collection 

 known to be H. incomptus (Meek) . Of the latter, Meek only described 

 the abactinal area, while Miller's specimen shows the actinal side. 

 The four specimens in the Harris collection unmistakably affirm 

 that both forms are identical, and since Meek's name has priority 

 it is here accepted. * 



For remarks as to the relationship of this species see H. matutinus. 



Through the kindness of Prof. George W. Harper, principal of the 

 "Woodward High School, Cincinnati, Ohio, the writer was enabled to 

 study the type of Palseaster darkana Miller." The specimen is a 

 little abraded, but shows all the characters of H. incomptus except that 

 it is much smaller in size. The abactinal area on a cursory examina- 

 tion shows but three columns, but in several places can be seen pro- 

 jecting small parts of the inframarginal columns. The disk also shows 

 the same general arrangement and number of plates as in H. incomptus. 

 There is therefore nothing except the smaller number of plates in the 

 columns to distinguish P. darkana from H. incomptus. Bearing 

 in mind that the former is but one-third the size of the latter, it is 

 not remarkable that P. darkana should have but 6 or 7 plates 

 while H. incomptus has 9 to 10 plates in the same columns. The 

 entire difference is accounted for when one regards P. darkana as 

 the young of H. incomptus. 



Another small but very poorly preserved specimen showing the 

 actinal area is in the Ulrich collection of the National Museum and 

 agrees with the type of P. darkana. Its measurements are: 

 11 = 4.5 mm., r = 2 mm., K = 2.2r. 



The only ontogenetic character observable in these small speci- 

 mens of H. incomptus is that the columns have fewer ossicles, and the 

 same is true of the abactinal area of the disk. It has a central disk 

 plate, the first ring of small plates and the second ring of basal radial 

 and interradial plates. But no intercalated small plates radial in 

 position are present. The second ring of 10 plates and the central 

 plate are the most prominent. If one were theoretically to reduce 

 the size of the animal still more, the plates of the first ring would be 

 the first to go and the rays would be simultaneously very much 

 shortened, probably obsolete, resulting in a hemispheric nonstellate 

 starfish. The abactinal area seemingly will then have but a central 

 disk plate and 10 others, 5 radial and 5 interradial in position. On 

 the actinal side there will be but the 5 axillary marginal plates 

 separated from one another by the ambulacra! furrow and the 

 ambulacralia. This hypothetic animal therefore closely resembles 

 a very young Comatula without the stalk or column, and also the stage 

 of living asterids following the brachiolarial. 



Cat. Nos. 40882, 60616, 60617, 60618 U.S.N.M. 



50601 Bull. 8815 5 



