Dec, 1920] Cystids and Blastoids 49 



The third species, Holocysiites abnormis, differs from both the preceding 

 in having the intercalated plates inserted in a more or less transverse 

 row beneath the fourth series of plates, counting downward from the 

 top of the theca. Of these three species, Holocystites cyUndricus is 

 regarded as the genotype. 



The other three species, Holocystites winchclli, H. ovatus, and H. 

 scutellatus, are oval or approximately spherical in form, and to these 

 must be added H. sphcericus described by Winchell and Marcy from the 

 Racine of the Chicago area, and H. jolietensis described by Miller from 

 the Niagaran of Joliet, Illinois. 



Holocystites of Miller. — The 40 so-called species of Holocystites 

 described by Miller from the Osgood limestone of Indiana, one species 

 being cited as thovigh from the top of the Laurel limestone in the Waldron 

 area, all agree in having the plates pierced by diplopores, the pores of 

 each pair being connected just beneath the surface of the plates by 

 peculiar channels frequently resembling the Greek letter Omega. Both 

 the oral and the anal aperture have polygonal margins, the polygonal 

 outline of the oral aperture being accentuated by the food-grooves 

 leading from each angle of this aperture to the proximal end of a facet, 

 each facet evidently serving originally for the support of a brachiole, 

 since the food-groove indents the margin of each facet, although no 

 brachioles ever have been found. At least 10 of these species had 5 

 brachioles, 2 more species probably having the same number. At least 

 16 species had 4 brachioles, 5 additional species probably having the 

 same number of brachioles. 



Holocystites amplus group. — Of the remaining 7 species described by 

 Miller, 5 may belong to the group typified by Holocystites amplus. In 

 this group, 3 food-grooves, narrowing distally, lead from angles of the 

 oral aperture to large facets for the support of brachioles. The nearest 

 relative to Holocystites amplus appears to be Holocystites adipatus, which 

 preserves one of the long, rapidly attenuating food-grooves; Holo- 

 cystites tumidus resembles H. adipatus in shape, and H. ventricosiis may 

 belong here also. Holocystites gyriniis agrees apparently in having three 

 main food-grooves, but the latter do not attenuate strongly distally as 

 in H. amplus, and both the left and left anterior food-grooves appear to 

 bifurcate on reaching the facets, as though two arms were supported 

 on a single protuberance in each case. The facet at the end of the right- 

 hand ray is not preserved. Unfortunately, the upper end of the theca 

 has been crushed from front to rear, producing the tantalizing conviction 

 that some extremely interesting structure is here obscured. In the species 

 with 3 main food-grooves, the length of these grooves is so much greater 

 than in other species that there is a possibility of their belonging to a 

 distinct genus. It is not certain, however, that Holocystites gyrinus 

 belongs to the same group as Holocystites amplus, although the limitation 

 of the food-groove system in both cases to 3 main strongly divergent rays 

 suggests such a relationship. 



