526 REPORT ON ZOOLOGY, MDCCCXLIV. 



Pentacrinus caput Medusce is beset with cirri, verticillately 

 disposed with five in eacli whorl, whose distance apart and 

 length diminishes from below upwards. At the upper part 

 of the stem longer and shorter joints alternate. The upper 

 joints, which present five obtuse angles, grasp each other 

 with serrato-denticulate borders, whilst the joints at the 

 lower end of the stem, are connected by straight sutures. 

 The inferior many-jointed cirri of the stem present an 

 unciform, curved, terminal joint. The five rays of the cup 

 consist each of three pieces, the uppermost of which pre- 

 sents two articular surfaces for the attachment of the arms, 

 which are there affixed. In these arms, in Pentacrinus as 

 well as in the other Crinoideye, joints exist, which are not 

 connected, moveably, with the contiguous joints, either by 

 muscles or an elastic intercellular substance, but bv sutures 



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admitting of no motion whatever. Immoveable sutures of 

 this kind are termed by Miiller " syzygia." A joint below one 

 of these syzygia never bears pinuulpe. Otherwise the latter 

 alternate on the joints, and appear to be, in general, regu- 

 larly distributed. The abdominal surface [surface of the 

 stomach] of the Pentacrini and Comatulte is covered with a 

 soft perisoma, which connects the rays of the cup, and is 

 continued upon the free arms and pinnuloe. On this peri- 

 soma, both on the arms and pinnulne, run longitudinal 

 channels, which open into each other, pass from the arms 

 upon the cup, and terminate in a tentacular ring surrounding 

 the mouth. The edge of these channels is beset with delicate, 

 minute, cylindrical tentacles or cirri (Fuhleru), which have 

 the power of elongating or shortening themselves, and the 

 surface of which is again covered with more minute cylindri- 

 cal tentacules or cirruli (Fiihlerchcn). In the Comatulffi 

 the prnmilsB present saccular enlargements, which in some 

 individuals contain ova, and in others, on the contrary, sper- 

 matic corpuscles. 



