56 BULLETIN 88, UNITED STATES NATIONAL MUSEUM. 



The adopted genotype of Protopalseaster (P. narrawayi) is described 

 at length and in detail by Hudson, but, thinking the specimen 

 showed the actinal side, he described the ambulacrals as epineural 

 plates roofing over the ambulacral furrow, a character that he of 

 course recognized as wholly anomalous for starfishes. Raymond 

 later on showed that the actinal side of this specimen lies buried in 

 the rock and that the entire abactinal plates are now gone, so that 

 the view is of the actinal plates from their inner side, i. e., an inter- 

 nal view of the ventral skeleton (later Hudson combats this view). 

 Under these circumstances nearly all of Hudson's generalizations 

 are fallacious and especially his statement that "we are dealing 

 with an unrecognized and very archaic morphological type which 

 links the Edrioasteroidea with the Stelleroidea " (1912 : 24) . A proper 

 interpretation of the specimen shows it to be a primitive but other- 

 wise a normal early Paleozoic starfish. Even though Hudson's 

 genus is far better determined generically than that of Stiirtz, it 

 must give way to the older name Hudsonaster. No one regrets this 

 more than the writer, because the generic name Protopalseaster ex- 

 presses the phyletic relationship of these primitive starfishes and is a 

 name that he has had in manuscript for the past 15 years. 



Hudsonaster has its nearest known relationship in Palseaster, but 

 differs at once from the latter in that the rays have abactinally five 

 columns of plates, while Palseaster has but four. In other words, 

 Palseaster has no radial columns of ray plates, but their place is oc- 

 cupied by numerous small accessory pieces. The abactinal disk 

 of Palseaster is also quite different hi having numerous small acces- 

 sory ossicles, while in Hudsonaster this area is devoid of these pieces 

 and instead there are disk plates that are larger, far less numerous, 

 and with a definite arrangement. 



The plate arrangement of Hudsonaster is simple and primitive 

 in that it distinctly retains to maturity much of the larval plate 

 structure of recent species and does not develop accessory ambital 

 or accessory abactinal plates as do its descendants Mesopalseaster 

 and particularly Promopalseaster. In Hudsonaster the axils are 

 occupied by single, large, axillary marginals, against which rest 

 the columns of inframarginal plates of adjoining rays. In the other 

 two mentioned genera, interbrachial arcs begin to develop by crowd- 

 ing orally the axillary marginals, when, as in Mesopalseaster , the 

 proximal plates of the inframarghial series of adjoining rays abut 

 against each other. In Promopalseaster this crowding of the infra- 

 marginal plates into the interbrachial areas is continued, always a 

 pair of plates at a time passing orally. For other remarks on the 

 development and distinction between these genera, see Mesopalse- 

 aster and Promopalseaster. 



