274 PALAEONTOLOGY OF ILLINOIS. 



Locality and position : Hardin county, Illinois; St. Louis division of Lower 

 Carboniferous series. 



BLASTOIDEA. 

 Genus GRANATOCRINUS, Troost. 



Synon. — Mitra (sp.), Cumberland, 1826. Reliquiae Conservata?, p. 31 ; (notLam., 1799). 

 Pcntremites (sp.), Auct. — (not Say). 



Granatocrinus, Troost, 1850. List, Proceed. Am. Ass. Adv. Sci., Cambridge, 

 p. 62, without figures or description; Hall, Fifteenth Ann. Report Regents 

 Univ.N. Y., p. 146; Shumard, 1865, Cat. Pal. Foss.,part 1, Crinoidea, p. 375. 

 Pentatremites (sp.), Roemer, 1852. Blastoidea, p. 43; Sowerby and others. 



Body globose, oval or elliptic. Pseudo-ambulacral areas like 

 those of the genus Pentremites, excepting that they are propor- 

 tionally narrower, and extend nearly or quite the entire length 

 of the body. Basal pieces three, sunken in a concavity so as 

 not to be visible in a side view. Radial or fork-pieces gener- 

 ally shorter than in Pentremites, but otherwise similar; in terra- 

 dials comparatively large, sometimes more than half the length 

 of the body. Anal opening as in Pentremites; ovarian? openings 

 intimately connected with the interradials, or sometimes pass- 

 ing directly through the inner end of each of these pieces. 

 Arms and column as in Pentremites ; surface usually granular, 

 sometimes coarsely so. 



The generic formula of this group is exactly the same as that of Pentremites, 

 Say, so far as regards the number and arrangement of the pieces forming the 

 body, though the form and proportions of these pieces are so different as to give 

 a very different outline and general physiognomy to the entire fossil. They are 

 therefore readily distinguished from Say's genus, as properly restricted, by 

 their regular oval, elliptical, or subglobose form, concave or less protuberant 

 base, and much narrower and more elongated pseudo-ambulacral areas, which 

 extend the entire length of the body, so as to give it more the appearance of 

 an Echinoid. They likewise present differences in the arrangement of the 

 ovarian ? openings of the summit, which are more intimately connected 

 with the interradial pieces, being sometimes excavated, one into each lateral 

 margin of these pieces (6r. Sayi); or in other instances piercing directly 



