260 CATALOGUE OF THE BLASTOIDEA. 



elongated slits, which are separated by intervening ridges, and are excavated partly 

 in the truncated upper surfaces of the radials and partly in the deltoids. They are 

 subparallel to the ambulacra, the overlapping side plates of which may partially 

 conceal one or more of them. Mouth small. Anus large, ovate or rhombic. Column 

 small, composed of round or obscurely pentagonal joints. Ornament consisting of fine 

 lines arranged parallel to the margins of the plates. 



History. The genus Codaster was proposed by Prof. F. McCoy in 1849, and two 

 species were described by him from the Carboniferous Limestone of the North of 

 England. In 1851 Prof. F. Roemer altered the spelling of the name from Codaster 

 to Codonaster, in order to make it etymologically correct, and his emendation was 

 adopted by Prof. McCoy in the explanation of one of the plates of the ' British 

 Palaeozoic Fossils ' l . The name has been similarly spelt by Pictet, Bronn, Dujardin 

 and Hupe, and by other European palaeontologists, though we prefer to retain the 

 original spelling, as has been invariably done in America. The first species of Codaster 

 described in the lattter country was the C. alternatus of Mr. S. S. Lyon 2 , from the 

 Devonian rocks of Kentucky, and three years afterwards (in 1858), Dr. B. F. 

 Shumard 3 added two others, C '. pyramidatus and C. Americanus from similar horizons 

 in Kentucky and Ohio. In 1SG1, a fourth American species was described by Prof. 

 James Hall 4 from the Burlington Limestone, under the name of C. Whitei. It is 

 an ovoid form with narrow ambulacra. Hall says the interradii " appear to be com- 

 posed of separate linear plates, like the pectinated rhombs of Cystideans ; and in one 

 place, where broken through, they are seen to be disconnected almost to the inner faces 

 of the substance, giving the appearance of numerous thin parallel lamina?." McCoy 

 had already given a description of this structure in his generic diagnosis, which Hall 

 seems to have altogether ignored, and McCoy had further noted its absence in the 

 azygos interradius, a point to which Hall makes no reference. We are therefore 

 unable to determine from his description whether Codaster Whitei is properly so 

 named, or should be referred to Phwnoschisma. Hall's description of the hydrospires 

 was, however, an improvement on McCoy's, and foreshadowed the important 

 discoveries made by the late Mr. John Rofe, published in 1865. He found, by means 

 of thin sections prepared for the microscope, that the ridges on the striated inter- 

 radial areas " are the tops of a series of folds of a thin test or membrane ; the alter- 

 nate folds being so united at the ends, as to form a series of long, but very narrow 

 sacs." For these organs Rofe suggested a probable respiratory character 6 . In 1869 

 his views were adopted by the late Mr. Billings, who termed these tubular organs 



1 Op. at. riate 3 d. 



2 D. D. Owen's 3rd Report Gcol. Survey Kentucky, 1857, p. 493. 



3 Trans. St. Louis Acad. Sci. 1858, vol. i. pt. 2, p. 239. 



4 Boston Journ. Nat. Hist. vol. viii. p. 327. 



5 Geol. Mag. 18G5, vol. ii. p. 251. 



