1890.] NATURAL SCrENCES OF PHILADELPHIA. 371 



tichal space, all arranged horizontally. In DolatocrinHs the vascu- 

 lar system probably extended only over the peripheral portions, the 

 upper portions at the inner floor of the tegnien being perfectly 

 smooth. In Batocrimts and Teleiocrinus it passes up to the outer 

 margins of the orals ; while in Physetocrbiufi, in species in which the 

 orals are unrepresented, it extends over the whole inner surface. 



The subtegminal anal tube of SiphonoGrinus is yet unexplained, 

 and we freely admit the structure is still a puzzle to us, but in the 

 absence of specimens showing the test (we know it only from natural 

 casts), we abstain from any speculation respecting it. It should be 

 said, however, that in Siphonocrinus nohilis the tube passes out 

 centrally — not anteriorly — which leads to the conclusion that the 

 ventral structure of Siphonocrinus armosus cannot have been essenti- 

 ally different from that of the other Camerata. The so-called sub- 

 tegminal anal tube is probably the extended hind gut, which passed 

 over the mouth and portions of the ambulacra. It appears from the 

 impressions upon the casts that the individual plates, w'hich cover the 

 ambulacra and surrounding parts, extend also over the " proboscis." 



From the foregoing facts it appears that Batocrbms, Phyiietocrinus 

 and allied forms likewise had but one integument covering the body, 

 that the structure which was supposed to represent the " vault," is 

 composed merely of the outward growth of the plates constituting 

 the disk, and that the plates are thickened and project in " T " shaped 

 extensions. 



It will be remembered that it was upon these forms mainly that 

 we postulated the presence of a vault in all Camerata, but now, if 

 it is true that even these have no further integument covering the 

 disk, it seems to us conclusive evidence that a vault as a special 

 structure does not exist in any Crinoids whatever, and that the teg- 

 men in all of them is a greatly modified disk. 



A comparison of the earlier with the later Camerata shows that 

 in Silurian forms the ventral surface, as a rule, is covered by small, 

 irregularly arranged plates; that these gradually increase in size in 

 the Devonian, and attain in the Carboniferous that extravagance of 

 form, which in the Batocrinites and Actinocrinites reaches its cul- 

 mination. With regard to the aml)ulacra we have observed that in 

 the earlier forms they are much more frequently exposed, their 

 covering pieces are smaller, more regularly arranged, and not so 

 highly differentiated as in the later ones. Their disk generally re- 

 sembles that of recent Crinoids, and if it were not for the sutural 



