1> INSCRIPTIONS OF Till: SPECIES. 259 



Bydrospire-slits entirely visible, but none in the anal 1 ( , , .. ,, 



interradius. J 



Bydrospire-slits partially concealed by the ambulacra, 1 ]>/l(niflsr/l/ ^„_ ,, , & ( . 

 and present in the anal interradius. J 



Genus COUASTER \ McCoy, 1849. 



? "New Genus," Phillips, 111. Geol. York. pt. 2, 18:56, p. 208. 



Codaster, McCoy, Ann. & Mag. Nat. Hist. 1849, vol. iii. p. 250. 



Codonaster, Roemer, Archiv f. Naturgesch. 1851, Jahrg. xvii. 13d. i. p. 381. 



Codaster et Codonaster, McCoy, Brit. Pal. Foss. 1851, fasc. i. p. 122, t. 3d (expl. of). 



Codonaster, Roemer, in Bronn's Lethaja Geogn., Dritte Auflagc, 1852, Theil ii. p. 258. 



Codonaster, Pictct, Traite dc Pal. sec. edit. 1857, torn. iv. p. 295. 



Codonaster, Bronn, Klasseu und Ordn. Thier-Reichs, 1800, Bd. ii. p. 189. 



Codonaster, Dujardin & Hupe, Hist. Nat. Zoopli. Echinod. 1862, p. 101. 



Codonaster, Rofc, Geol. Mag. 18G5, vol. ii. p. 250. 



Codaster, Billings 2 , American Jouru. Sci. 1869, vol. xlviii. p. 78, 1870; ibid. vol. xlix. p. 5 I. 



Codonaster, Zittcl, Ilandb. Pal. 1879, 1 Bd. 3 Lief. p. 424. 



Codaster, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 230. 



Heteroschisma, Wachsmuth, Report Geol. Survey Illinois, 1883, vol. vii. p. 352. 



Heteroschisma, Wachsmuth, Proc. Davenport Acad. Nat. Sci. 1885, vol. iv. p. 82. 



Gen. Char. Calyx inverted conical or pyramidal, sometimes ovoid ; base obtusely 

 trilobate, or tapering to a more or less acute point ; summit usually broad, sometimes 

 abruptly truncated and flattened, or gently convex, and presenting a stellate appearance, 

 which is due to the alternation of the radiating oral ridges with the ambulacra ; section, 

 as a rule, distinctly pentagonal ; periphery variable in position, but always nearer to the 

 summit end of the calyx. Basal plates forming a conical or triangular cup, usually 

 deep. Radial plates large, the proximal ends always more or less bent inwards 

 horizontally "to assist in forming the summit, and never deeply excavated by the 

 sinuses. Deltoid plates wholly confined to the summit, four of them irregularly 

 triangular, and bearing prominent, convex, lanceolate oval ridges ; the fifth or anal 

 deltoid more triangular than the others, devoid of a ridge and pierced by the anus. 

 Ambulacra petaloid, or narrow and linear ; lancet-plates, as a rule, deeply excavated 

 for the side plates. Spiracles absent. Hydrospires pendent, in eight groups, 

 suspended vertically within the calyx, two in each of the four regular interradii, but 

 wanting in the azygos one. The tubes open externally by a variable number of 



1 There is no doubt that Codonaster is etymological!)- more correct than Codaster, as pointed out by 

 Roemer. As in the cases of Ptntremites and Troostocrinus, however, we use Codaster on the principle of 

 plurimorum auctorum. 



2 For the same paper, see also Canadian Nat. and Geol. lS'lH, vol. iv. pp. 2>7 and 429; Ann. & Mag. 

 Nat. Hist. 1870, vol. v. pp. 261 and -412. 



2 l2 



