122 BRITISH PALAOZOIC FOSSILS. [EcuinopEeRMata. 
cup crossed by two to four ridges running towards the centre of each adjoining plate, and the interval at the 
corners sometimes filled with angularly bent ridges. Length of body, from the scapulze or 3rd primary radials to 
base of pelvis, one inch; width one inch three lines. 
The column of this abundant species is round, formed, near the pelvis, of thin joints, alternately a little 
longer and thicker, every third or fourth joint larger; nearer the base the joints become of an uniform thickness 
and size; when young they are contracted at the sutures, so as to be slightly moniliform; the articulating 
surface is regularly striated from the centre; round auxiliary side-arms come off irregularly from the columns ; 
the plates of the body generally exhibit very distinctly the marks of muscular contraction, in the form of strong, 
variable, radiating ridges. The fingers are formed, as usual, of two series of joints. 
Position and Locality—Carboniferous limestone, Bolland. 
2nd Ord. BLASTOIDEA. 
Body enclosed in a cup of few, thin, calcareous plates ; fixed by a small jointed stem to foreign bodies ; five 
rows of pseudambulacra, extending from the mouth in the middle of the upper aspect towards the base, set with 
small jointed tentacles in place of suckers or arms. 
Genus. CODASTER (A7°Coy). 
Ref—M Coy, Ann, Nat. Hist. 2nd Series, Vol. III. p. 250. 
Gen. Chav.—Cup conical, with the upper part broad, flat, truncate ; pelvis deep, conical, of three pieces, 
one tetragonal and two pentagonal, each having its inner apex notched to form part of the round columnar 
canal; on the upper edges of these rest five large equal first supra-basal plates which reach to the truncated 
summit, to which, from their mesial gibbosity, they give a pentagonal outline ; in the centre of this superior disk 
the mouth seems situated, and from it five prominent, minutely porous pseudambulacra diverge, one to each 
angle, each being placed on a thick tapering ridge divided by a mesial sulcus; from the re-entering angles of 
these ridges four other thick, rapidly tapering ridges proceed, one to the middle of each of four of the straight 
sides, each ridge at its thick, oral end, shews an obscure impression; the fifth space is without a ridge, being 
occupied by a large, ovate or lozenge-shaped (? anal) opening; the depressed, triangular intervening spaces 
are marked with coarse, rough parallel striz nearly coinciding in direction with the pseudambulacral ridges, 
and converging to the second set of ridges; the impressed lines between these strize seem punctured ; the fifth 
(2 posterior) space is without sulcation. 
These strange and beautiful forms, the “ bell-stars,” as they may be called, are obviously allied to Pentre- 
mites (taking P. Derbiensis, florealis, oblongus, ellipticus, and such like, as the types of the genus), from which 
they differ in having the small basal plates enormously developed into a conical pelvis, and having the pseudam- 
bulacra entirely confined to the capital plates (which here form a truncated disk), instead of being continued 
through a slit in the supra-basal plates nearly to their base. The peculiar sulcation, represented in our figures 
in four of the interambulacral spaces, resembles that of some Cystidea, but is unlike anything in Pentremites. 
I cannot find any trace of the four small ovarian pores, although the large opening above mentioned holds the 
place of the fifth or great posterior ovarian pore of the Pentremites and the Echinida ; it will also be observed 
that it holds the place of the mouth of certain Platycrini. In Prof. Forbes’s paper on the British Cystidea 
in the second volume of the “ Memoirs of the Geol. Survey,” p. 529, there is a figure representing “the pro- 
jection of the arm-bearing surface of the Pentremites pentagonalis,” which resembles the disk of our genus 
except in having the posterior interambulacral space sulcated, and with a thick mesial ridge like the rest; 
I do not suppose that that figure is meant to represent the Platycrinus pentagonalis of Miller, forming the 
Pentremites id. of G. Sowerby and Phillips, which presents no resemblance of the kind. I only know the 
following two species, from the carboniferous limestone. 
