METAZOA ECHINODERMA. 157 



the grooves have become filled with solid matter, but the 

 position of the parts is well shown. The branching of 

 the arms on leaving the body is seen in another cast, No. 

 2776, where the aboral side is uppermost. 



From the oral disc extended a long anal tube. This 

 is seen in No. 277 a, while its position is indicated in the 

 casts. Respiration was probably effected in Actinocrinus 

 by tentacles on the edges of the ambulacra. 



Marsupiocrinus (No. 278, M. caelatus Phil.) has a lower 

 oral vault than Actinocrinus, and it is composed of a larger 

 number of plates than usually is found. The arms are 

 provided with pinnules (No. 278) but are unbranched. 

 Similar in general structure to Marsupiocrinus is Eucalyp- 

 tocrinus caelatus Hall (No. 279). This Crinoid when full 

 grown had a large, plump, complex body, which was con- 

 cave at the bottom, the basals and in some cases the radi- 

 als extending upward and forming a cone. The arms are 

 comparatively small, set in deep recesses (No. 279), and 

 the ambulacra have the same structure as in Actinocrinus. 

 Here the anal tube was very long and large. 



Apiocrinus (No. 280) differs from the preceding in that 

 the stem forms a portion of the body. These two parts 

 can always be distinguished from each other, as the por- 

 tion corresponding to the body of other Crinoids has 

 vertical and oblique lines, while the stem portion has only 

 circular lines, dividing it into horizontal discs. The 

 ambulacra are uncovered, and there is no vault or anal 

 tube. 



Millericrinus mespiliformis d 'Orb. (No. 281), is similar 

 to Apiocrinus in some respects. As a general thing both 

 have the stem enlarged, but that of Millericrinus widens 

 more gradually, and the upper joint is not much larger 

 than those below it. Recently, vestiges of underbasals 

 have been found in two species of this genus, and in both 

 cases these plates had separated from the basal and be- 

 come attached to the top stem joint (No. 281). 



Most of the forms of Crinoids already described have 



