MORPHOLOGICAL PART. 107 
integument was regarded as a structure sai generis, to which the term “vault” 
was applied. The inner integuinent appears at first sight as if composed of 
independent, ill-formed pieces; but on closer inspection it is found that 
these so-called plates are extensions from the plates above, and continuous 
with them. Each lower part is connected with the corresponding upper one 
by small surfaces or pillars, and joining by its edges with other like plates, 
leaves open spaces or meshes along the sides. The inner portions constitute 
a kind of internal lining or network, extending from the first costals and first 
interbrachials uninterruptedly to the margins of the orals. In some speci- 
mens only the pillars are preserved, the lateral extensions of the plates being 
wanting ; while in others the floor is almost entirely smooth. The latter is 
the case in Cactocrinus proboscidalis (Plate V. Fig. 10); while in Teleioerinus 
rudis (Plate V. Fig. 16), and in the specimen of Doryerinus (ibid. Fig. 15), the 
grooves are formed into well defined tunnels. A further indication that there 
were probably two integuments in some of the Camerata at least, seemed 
to be presented by the ventral structure of Siphonocrinus armosus from the 
Niagara group (Plate XIX. Figs. 5 a, b,c). This species, so well known from 
natural casts, has a large, trumpet-shaped, subtegminal anal tube, which 
crosses the mouth, overlies the upper ends of the ambulacral tubes, and is 
continued subtegminally all the way to the anterior side of the calyx, even 
beyond the arm regions, where it bends outward. The case is best. illus- 
trated if we imagine the disk of a recent Crinoid, with an anal tube like 
that of Antedon regals (Chall. Rep. on the Comat., Plate XLVI. Fig. 2), 
extended all the way out to the arm bases of the anterior ray, and covered 
by a vault. 
It seemed hard to account for the facts presented by these cases, except by 
the presence of two distinct structures covering the body cavity ; and upon 
these specimens principally we formed the opinion, in the first instance, that 
the Camerata had a vault and a subtegminal disk, and that the vault was 
a structure without a parallel in recent Crinoids. The evidence appeared 
to be conclusive that the disk was subtegminal, in some groups at least, and 
this, which had been generally acknowledged by leading authors, led us to 
believe that in all Camerata the disk was roofed over by a vault. In fact 
this conclusion seemed to be corroborated by the nature of the plates, which, 
although varying considerably in size and number, are arranged in all these 
Crinoids on the same general principle, forming in all of them a compact, 
rigid test, with the mouth and food grooves perfectly closed. 
