268 CATALOGUE OF THE BLASTOIDEA. 



(Presented by Prof. H. A. Nicholson, M.D., &c.). [Kentucky, fide Wachsmuth ; New 

 York State, fide Hall : Upper Helderberg Limestone, Lower Devonian.] 



2. SPECIES FROM THE CARBONIFEROUS. 

 b. Ovate Species. 



CODASTER TRILOBATUS, McCoy. 



(PI. XII. fig. S ; PI. XIII. figs. 1-15 ; PI. XVIII. fig. 1.) 



Codaster trilobatus, McCoy, Ann. & Mag. Nat. Hist. 1819, vol. iii. p. 251. 



Codaster trilobatus, McCoy, Brit. Pal. Foss. 1851, fasc. 1, p. 123, t. 3 d. f. 8 & 8 a {Codonaster 



in expl. of plate). 

 Codonaster trilobatus, Rocmcr, Archiv f. Natnrgesch. 1851, Jahrg. xvii. Bd. i. p. 386, t. 8. 



f. 3, a & b. 

 Codonaster trilobatus, Dujardin & Hupo, Hist. Nat. Zooph. Echinod. 1862, p. 102. 

 Codaster trilobatus, E. & C, Ann. & Mag. Nat. Hist. 1882, vol. ix. p. 235. 



S'j). Char. Calyx ovate or cup-shaped, formed by thick, strong plates, and tapering 

 very slowly towards the base, which is always more or less trilobate, one extreme 

 assuming the form of a flattened tripod, whilst in another these divisions do not 

 descend low enough to become marked, and the base is more acute ; summit 

 truncated, and either flat or slightly convex ; section pentagonal, the sides of the 

 calyx flat, or a little convex ; periphery at about one half the height of the radial 

 plates. Basal plates obtusely lobate towards their lower margins, forming, when in 

 union, a broad expanded cup ; interradial sutures placed in depressions. Radial 

 plates longer than wide, the limbs bent inwards horizontally to form the flat summit ; 

 interradial sutures in slight depressions ; sinuses narrow and very short, and wholly 

 excavated out of the summit portions of the plates. Deltoid plates diamond- or 

 lozenge-shaped ; oral ridges strong, and convex or subcristifonn. Ambulacra peta- 

 loid, short, projecting above the radio-deltoid margins ; food-grooves wide and deep, 

 excavated in the lancet-plates for nearly the whole length of the ambulacra ; sides 

 of the lancet-plates deeply impressed for the reception of the side plates, which are 

 eight to ten in number (sometimes meeting in the middle line at the distal ends of 

 the ambulacra). Six to ten hydrospire-slits, one of them usually covered by the 

 ambulacrum ; hydrospire-tubes long and much compressed; sacs hardly differentiated 

 from them. Column round, stem-joints small. Ornament of fine raised subimbri- 

 cating lines, parallel to the margins of the plates. 



Remarks. With the exception of the original description by McCoy, and that 

 subsequently given by Roemer, little appears to have been written about either 

 C. trilobatus or its variety acutus. Although a number of specimens are contained 

 in the "Gilbertson Collection," which illustrates the second part of the ' Illustrations 

 of the Geology of Yorkshire,' by the late Prof. John Phillips, that author does not 



