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The comparatively large abdominal cavity of the Crinoidea inarticulata, its 

 protection by plates, and their slender connection to the column, seemed to 

 indicate that an analogous animal might exist in nature without being provided 

 with a column or organs of permanent attachment, and therefore capable of 

 locomotion. I at first apprehended that this might be detected iu the Euryale, 

 but soon found that a greater conformity in organic construction ought to exist, 

 before the transition or link could be considered as perfect. I therefore again 

 referred to the general conclusions resulting from my previous inquiries rela- 

 tively to the Crinoidea, of which it will be necessary in order to guide our fur- 

 ther progress to subjoin in this place the following brief recapitulation. 



The Crinoidea are animals provided with a column formed of numerous 

 joints, surmounted by five articulated arms, which enclose between them at their 

 base the viscera in a cuplike cavity. 



The portion that encloses the viscera, although it may be considered as a 

 beginning of the arms, yet by being laterally connected is deprived of expan- 

 sion, or rather possesses it only in a very limited degree; hence it varies its 

 figure in conformity to the size of the viscera, which viscera must be again con- 

 formable (in accordance to general Zoological principles) to the nature and 

 quantity of food requisite to the animal economy. 



It is this conformity of the exterior covering to the viscera, which, perhaps, 

 chiefly occasions the gradual transition from articulating joints (Crinoidea arti- 

 culata) to plates adhering only by sutures (Crinoidea inarticulata.,) 



The analogy between joints and plates at the base of the arms, is preserved 

 by the similarity in position and number of those pieces which in both cases 

 have been denominated as costals and scapulae, as in the Crinoidea articulata, 

 and the genera Actinocrinites and Rhodocrinites, of the division Crinoidea 

 inarticulata. 



The muscular action extended from the pelvis to the arms, is transmitted in 

 a similar manner in all the Crinoidea, only that in one instance (the articulata) it 

 is effected from joint to joint by means of attachment to the articulations, and 

 iu the other (the inarticulata) over the plates by means of adhesion and sutural 

 attachment. 



