58 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



distal portion of the column I think we may well assume that a 

 detached existence was largely maintained within tliis family. 



Homocrinus scoparius. — In Homocrinus scoparius cirri are borne for 

 a considerable distance along the distal portion of the column. These 

 cirri are short and feeble, and both because of their extent and their 

 structure may not be held as roots. In well preserved specimens it 

 will be noted that the extreme distal portion of the column is coiled J 

 into several volutions. Such a stem is figured by Talbot. (1905, pi. 

 3, fig. 3.) It seems highly probable from the structure of stem in this 

 species that a detached existence was maintained. In an earlier spe- 

 cies of the genus the distal coiling is perhaps even more marked, but 

 there is no sign of the presence of radicular cirri. 



Camptocrinus. — In Camptocrinus, which simulates to a remarkable 

 degree the column structure of Herpetocrinus heretofore described, 

 we may perhaps predicate a detached existence on the basis of this 

 similarity alone. Furthermore, a careful examination of a large 

 number of well preserved individuals of the genus has failed to show 

 any signs of permanent distal fixation. The functions of the cirri 

 in this genus may be held as similar to those of Herpetocrinus. 



The Platycrinidse. — Among the Plat3^crinid8B there is a certain com- 

 pact assemblage of types marked by such forms as Hapalocrinus and 

 Cordylocrinus in which the presence of verticils of cirri strongly point 

 to the conclusion that these forms were free. I have examined hun- 

 dreds of examples of Cordylocrinus and seldom have found the column 

 greatly to exceed the height of the crown. There is no sign of per- 

 manent fixation. Where the preservation justifies an opinion it 

 seems that the column ends distally with a cirriferous nodal, after the 

 manner of the Pentacrinidse. In Cordylocrinus plumosus the cirri 

 reach an extraordinary length. In some cases those cirri borne by 

 the proximal nodals reach beyond the tips of the arms. The presence 

 of verticils of cirri may in any case be held as strongly indicative of 

 the eleutherozoic habit of the animal to which they belong. Such 

 an excessive development of these appendages points almost with 

 certainty to this conclusion. 



Evidence relative to widespread detachment among the stalked Gri- 

 noidea. — The list of stalked crinoids which probably maintained a 

 detached existence might largely be increased. A sufficient number 

 of cases has been adduced, however, clearly to show the prevailing 

 tendency to be noted among the Crinoidea. Examples have been 

 chosen from each order and from widely dissimilar families. If a 

 detached mode of life obtains among these divergent types uniformly 

 and not as the result of fortuitous disruption, we may well expect 

 among other related families and genera that a similar tendency is 

 manifest. It rarely, if ever, is found that in a relatively homoge- 

 neous group like the crinoids any decided departure from the normal 



