PALEONTOLOGIC CONTRIBUTIONS 33 



Devonaster eucharis (Hall) 

 Plate S, figures i and 2; plate 9, figures 1-6 



This species has been very elaborately described and beautifully 

 figured by Hall in the 20th Report of the New York State Museum. 

 Additional observations have been made by Cole, Schondorf, Clarke 

 and Schuchert, so that the species appears to be known to the least 

 details of its ossicles. The wonderful find of hundreds of speci- 

 mens of this hitherto rare species in the Hamilton sandstone at 

 Saugerties, however, still permits us to add a few observations, 

 especially regarding the growth stages. 



From the detailed study of our material we have nothing to add 

 to the description of the species, as brought up to date and corrected 

 by Schuchert in his excellent Revision of the Paleozoic Steller- 

 oidea. 1 It is, however, apparent that Hall's description and those 

 of his successors, which are based mostly on the casts of his types, 

 are taken from specimens that are not only larger by one-quarter 

 to one-third than those from Saugerties which all possess a fairly 

 uniform size, but which also exhibit when compared with the latter, 

 certain differential features attributable to greater individual age. 

 We therefore believe that either the Saugerties specimens should be 

 described as a new variety of more youthful aspect, since on account 

 of their fairly uniform size they would seem to have reached 

 maturity — if one will not assume that they represent a wandering 

 swarm of individuals of a certain adolescent growth stage — or 

 that they should be considered as representing the real mature type 

 of Devonaster eucharis, and Hall's types as gerontic 

 individuals. We prefer the latter view in the present state of our 

 knowledge because it avoids the giving of a new name, although in 

 view of the remarkable fact that not any of the many Saugerties 

 specimens comes near the size of the few specimens available to 

 Hall, it is quite possible that we have de facto two varieties of 

 different size and stage of phylogenetic development before us. 

 However that may be, we will point out only the differences and 

 by comparison with a few very young specimens also obtained at 

 Saugerties, ascertain the changes attributable to individual growth. 



The principal difference is seen in the development of the acces- 

 sory plates on the abactinal (dorsal) side. In Hall's type' the 

 abactinal central area is filled with a pavement of minute accessory 

 plates or granules. " In the center of the disk is a plate somewhat 



1 Schuchert. Op. cit. p. 98. 



