46 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41.' 



Ancyrocrinus. — Under the name Ancyrocrinus (pi. 5, fig. 9) Hall 

 (1862) described a curious column from the Hamilton. The distal 

 extremity of the stem is rounded off smoothly. A short distance 

 from the end is typically to be found a verticil consisting of four 

 spur-like appendages. These spurs may be short and stout, as is 

 characteristic of the Hamilton of southern Indiana, or long and 

 slender, as is shown by the New York specimens. They are perforated 

 through the center by a very small canal which apparently does not 

 communicate with the exterior. 



At times the spurs depart from the normal arrangement, where all 

 are in the same plane, and are variously situated at different levels. 

 Occasionally more than four are present. However disposed verti- 

 cally, their relative peripheral arrangement is the same, the orienta- 

 tion conforming to that of the axial canal.. The spurs are directed 

 upward, and when but four are present the resemblance to a grapnel 

 is very marked. It is obvious that these spurs are modified radicular 

 cirri, in which all traces of the original segmentation as a rule have 

 been obliterated by a secondary deposition of stereom. 



Bather (1900) refers to Ancyrocrinus as the anchor of Myrtillo- 

 crinus. This reference is quite unsupported by known facts. Myr- 

 tillocrinus is found in America in the Onondaga limestone where no 

 signs of Ancyrocrinus have ever been seen, while in the Hamilton, where 

 Ancyrocrinus is fairly abundant, no trace of Myrtillocrinus has yet 

 been found. Moreover, the stem of Ancyrocrinus is quadrangular in 

 cross section, while that of Myrtillocrinus is round. Furthermore, 

 the size of these grapnels and that of the column is out of all propor- 

 tion to that of any known Myrtillocrinus theca. 



We may hold, I think, that this grapnel of Ancyrocrinus served 

 rather as a drag and ballast than as a true anchor. In a quiet sea, 

 the annual no doubt was steadied and maintained m a fairly stable 

 state by the weight of the terminal organ. If affected by current or 

 wave activity, however, the grapnel might be dragged along the bot- 

 tom and aid appreciably in controlling the motion of the animal. As 

 will be noted subsequently, it is quite conceivable that the Paleozoic 

 stalked Crinoidea, as well as then' modern representatives, often lived 

 well within the zone of wave activity. Under such conditions the 

 advantage of such a drag is immediately obvious. 



Megistocrinus or Dolatocrinus . — In connection with the curious 

 grapnel of Ancyrocrinus should be noted certain columns found in the 

 Hamilton group of New York State. These columns are referable 

 either to Megistocrinus or Dolatocrinus in all probability. In these 

 cases, the animal seems to have been detached as the result of a vio- 

 lent disruption. The break took place above the radicular cirri, if 

 such were present, for there are no signs indicative of such cirri on 

 the columns as preserved. The size of the column and its uniform 



