KEVISIOISr OF PALEOZOIC STELLEEOIDEA. 59 



the former differs in the wider ambulacral grooves. The difference 

 of greatest value, however, is found on the abactinal area of the 

 disk. In both species there is a central disk plate surrounded by a 

 ring of accessory plates. In H. matutinus there are eight plates in 

 this ring and in H. incomptus there are seven. Between all the basal 

 radials in the latter species there is an accessory plate, or these are 

 five in number, while in the former there are only two such plates. 

 Again, the proximal plates of the supramarginal columns in H. 

 incomptus are larger than any others of the abactinal area, while in 

 H. matutinus they are smaller than the basal radials and their form 

 and ornamentation are quite different. The madreporites are also 

 quite different. In general, H. incomptus is larger, stouter, the rays 

 broader and the disk has a greater number of accessory pieces. These 

 features are still more pronounced in H. rugosus (Billings). Viewing 

 these differences developmentally, the distinctions are slight, which 

 proves the three forms to be genetically related, but specifically the 

 differences are sufficiently marked to be regarded both morpholog- 

 ically and geologically as of specific value. 

 Apotype.Csii. No. 60603, U.S.JST.M. 



HUDSONASTER NARRAWAYI (Hudson). 



Plate 1, fig. 1; plate 2, fig. 1; plate 4, fig. 1. 



Protopalseaster narrawayi HUDSON, Ottawa Naturalist, vol. 26, 1912, p. 25, pis. 

 1-3; vol. 27, 1913, pp. 77-84, pis. 8, 9. RAYMOND, Ottawa Naturalist, vol. 26, 

 1912, pp. 105-107. HUDSON, Bull. N. Y. State Mus., No. 164, 1913, pi. 5 

 SPENCER, Mon. Brit. Pal. Asterozoa, pt. 1 (Palseontogr. Soc. for 1913), 1914, 

 p. 21, fig. 19. 



Description. Specimens small, an average individual from St. 

 Paul, Minnesota; measuring: R = 5 mm., r = 3 mm., R = 1.6r. Width 

 of ray at base 2.7 mm. The three good specimens show only the 

 actinal side while the fourth free siliceous one is too poorly preserved 

 to make out more than the form. 



Inframarginal columns have from 6 to 9 plates, while the adambu- 

 lacrals and ambulacrals each have from 11 to 12. Ambulacral plates 

 large and solid, rectangular, with slightly rounded ends. As these 

 plates are not t- -shaped as in other species of this genus it may be 

 shown that this character is of generic value, in which case Proto- 

 pal&aster will have to be revived. 



Inside of each of the large axillary plates lies a pair of oral armature 

 pieces that are in form very much like the adjoining adambulacrals. 

 From beneath these ossicles projects a stout and long, rounded, arma- 

 ture rod, the torus (a tooth or chisel), the 5 teeth meeting together 

 in the center of the mouth. These armature rods and more especially 

 the 10 pairs of ambulacral armature pieces are seldom seen in fossil 

 starfishes, and none shows it more clearly than the Yale specimen 



