142 BULLETIN 88, UlSTITED STATES NATIONAL MUSEUM. 



another axil, while two of the axils do not show any such intercalated 

 plates or granules. In one of the rays, at least, the ambulacral, adam- 

 bulacral, and marginal plates are distinctly visible, without inter- 

 calated plates on either side. 



"The presence of these unequally distributed plates or granules 

 is apparently an abnormal structiu-e, probably the result of accident 

 during the growth of the animal; and this view is sustained by the 

 fact that the other parts have the ordinary structure of Palseaster, 

 and in all other respects the specimen agrees with the typical Palse- 

 aster matutina.'' 



The holotype was examined by the writer and although imperfect 

 was found to have a normal development, with the plates in their 

 proper places in at least two of the rays and axils. It certainly is not 

 an abnormal development of "Palseaster Tnatutina" but represents 

 a normal individual of a distinct genus and species diverging from 

 Hudsonaster matutinus toward the forms with large disks and great 

 axillary areas, as in lAndstromaster and Palasterina. Hall seemingly 

 was led to make the erroneous remarks above quoted through the 

 fact that BUlings had also included in his description and illustration 

 (36) an individual of Hudsonaster matutinus, an error due to the 

 undoubtedly close relationship of this form with Petraster rigidus. 



PETRASTER SPECIOSUS (MiUer and Dyer). 



Plate 23, figs. 5-7; plate 26, fig. 1; plate 27, figa. 1-4. 



Palseasterina spedosa Miller and Dyer, Joum. Cincinnati Soc. Nat. Hist., vol. 1, 

 1878, p. 30, pi. 1, fig. 7.— Miller, N. Amer. Geol. Pal., 1889, p. 266, fig. 381. 



Palseasterina approximata Miller and Dyer, Journ. Cincinnati Soc. Nat. Hist., 

 vol. 1, 1878, p. 30, pi. 1, fig. 8. 



Original description of Palseasterina spedosa. — "Pentagonal; rays 

 obtuse at their apices; greatest distance from point to point about 

 2 J inches; breadth of body between rays about IJ inches, and dis- 

 tance from tip of ray to next adjoining tip on either side about 1^ 

 inches. 



"The [infra] marginal plates are small and somewhat hemispher- 

 ical near the termiaation of the rays,, they gradually enlarge and 

 become square, and then rectangular as they approach the disk, until 

 at the narrowest part of the disk or body of the fossil they are twice 

 as long as wide. There are about 50 marginal plates between the 

 apex of one ray and the next one adjoining, or, in a perfect specimen 

 of this size, about 250. 



"The back or dorsal side is covered with numerous plates (prob- 

 ably in a complete specimen of this size there would be 1,000 or more), 

 which are very prominent in the center or somewhat conical, and 

 seem to have been joined together with deeply serrated edges. 

 The plates have from three to eight of these indentations, which 

 give them a beautiful starUke appearance. 



