224 CATALOGUE OF THE BLASTOIDEA. 



would be the earliest species of the genus, unless the Pentremites Sampsoni of 

 Hambach from the underlying Chouteau Limestone, or Shumard's P. Missouriensis 

 should prove to be a Schizoblastus. The latter was referred by Shumard to the 

 Chemung Group of the Upper Devonian ; but Messrs. Meek & Worthen have given 

 reasons for thinking that the beds in Missouri, which Shumard regarded as Devonian, 

 are really of Subcarboniferous age, so that it is extremely doubtful whether Schizo- 

 blastus can be regarded as a Devonian genus. "We know of no species of it above 

 the Burlington Limestone, with the possible exception of Granatocrinus granulosus, 

 M. and W., which occurs in the Keokuk Limestone of Indiana and Illinois. 

 Type. Pentremites Sayi, Shumard. 



Schizoblastus Sayi, Shumard, sp. 

 (PL III. figs. 1-3 ; PL VI. fig. 18; PL X. fig. 17; PL XVII. fig. 1.) 



Pentremites Sayi, Shumard, in Swallow's 1st & 2nd Ann. Report Geol. Survey Missouri, 



1855, pt. 2, p. 185, t. B. f. 1, a-d. 

 Granatocrinus Sayi, Shumard, Trans. St. Louis Acad. Sci. 1865, vol. ii. no. 2, p. 370. 

 Granatocrinus Sayi, Meek & Worthen, Proc. Acad. Nat. Sci. Philad. 1869, p. 84. 

 Pentremites Potteri, Hambach, Trans. St. Louis Acad. Sci. 1880, vol. iv. no. 1, p. 156, 



t. B. f. 4, 

 Granatocrinus Sayi, Wachsmuth & Springer, Proc. Acad. Nat. Sci. Philad. 1881, 



t. xis. f. 3. 

 Schizoblastus Sayi, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 246. 



Sp. Char. Calyx subglobose or occasionally somewhat ovoidal ; summit flat, or a little 

 concave, and constricted like the base, which presents almost a plane surface, the calyx 

 resting conjointly on the basal plates and radial lips, or sometimes on the latter only ; 

 section circular, or slightly pentagonal, the interradial area not divided by deep 

 grooves ; periphery equatorial. Basal plates small, flattish, sometimes a little 

 concave, or slightly protuberant, but when so, hardly extending below the level of 

 the lips, and only very slightly perceptible in a side view ; basiradial sutures faintly 

 marked. Radial plates quite short, wider than long, forming only about a fourth of 

 the calyx ; bodies reduced to a minimum ; limbs short and broad, almost flat-sided, 

 or even a little concave ; sinuses moderately broad, with erect margins ; lips promi- 

 nent, forming a quinquepod on which the calyx rests ; interradial sutures in slight 

 depressions. Deltoid plates very large and long, elongately rhombic and forming 

 quite three fourths the entire length of the calyx, thicker than the radials, and 

 deeply pitted at their central ends ; the sides of each plate are obtusely rounded, 

 but the eminences thus formed become narrower towards the base, and leave between 

 them a central triangular depression, which is traversed in the middle line by an 

 obtuse ridge originating behind the depression of the constricted apex ; radio-deltoid 

 sutures obliquely arched, and usually deeply depressed. Ambulacra nearly parallel- 



