REVISION OF PALEOZOIC STELLEEOIDEA. 207 



SCHCENASTER (?) MONTANUS Raymond. 



Plate 33, fig. 5. 



SdiMnaster f montanus RAYMOND, Ottawa Naturalist, vol. 26, 1912, p. 80, fig. 

 3 on p. 81. 



Original description. "Animal small, about an inch in diameter. 

 Rays short, slender, extending about one-half their length beyond 

 the disk. Disk large, pentagonal, the margin slightly concave 

 between the rays. The five proximal plates of the adambulacral 

 series function as orals, while on the arms beyond the disk the adam- 

 bulacrals become marginals. The adambulacral plates are rather 

 small, oval, placed with the long axis diagonal to the axis of the arm. 

 On the most perfect arm there are 16 of these plates on each side of 

 the groove, not counting the proximal and distal plates. 



"The ambulacral ossicles are small, arranged alternately. On 

 this specimen they are mostly displaced. The plates on the disk 

 between the rays are few and small. The marginals are small, 

 rounded, and do not appear to bear spines, but this appearance may 

 be due to poor preservation. 



" Locality. This species is described from a single specimen col- 

 lected by the writer in the Madison limestone at Spring Canyon in 

 the Ruby Mountains, near Alder, Montana. The type is in the 

 Carnegie Museum, Pittsburgh, Pennsylvania." 



PAL^EOSOLASTERID^E, new family. 



Specialized multiradiate Cryptozonia with as many as 29 rays, 

 large disk, and actinal madreporite. Ambulacralia opposite or slightly 

 alternating. 

 Contains : 



Palseosolaster Stiirtz. 

 Echinasterias Sttirtz. 

 Echinodiscaster Delage and Herouard. 

 Echinostella Stiirtz. 

 Medusaster Sttirtz. 



How rays are introduced in multi-rayed asterids. For paleontologic 

 purposes it is not necessary to go deeply into this matter, 'but it is 

 desirable to know when, where, and how the supernumerary rays are 

 introduced in living forms so that we may be guided in our generic 

 studies. 



Ritter and Crocker 1 have recently summed up what is known on 

 this subject, and to their paper the reader is referred for further 

 study. 



In nearly all cases the multi-rayed forms have the rays of equal 

 development, and for this reason it is the general belief that 



i Ritter and Crocker, Multiplication of rays and bilateral symmetry in the 20-rayed starfish, Pycnopodia 

 kelianthoides (Stimpson), Proc. Washington Acad. Sci., vo . 2, 1900, pp. 247-274. 

 50601 Bull. 8815 14 



