68 



vault was never ventral to the body of the animal, nor was the 

 calyx dorsal to the body of the animal. The words ventral and 

 dorsal cannot be applied to a crinoid, in this way, with any more 

 reason than the roof of a house can be called the ventral side and 

 the cellar the dorsal side. The crinoid stood upright, and all the 

 organs were in that position, except the ovarian pores and 

 ambulacral canals, from the base of the arm to the ring surround- 

 ing the top of what Meek called the "convoluted organ." One 

 side was evidently anterior and the other posterior, and we have 

 no doubt that the azygous side is the anterior side and the op- 

 posite one posterior. Looking at the crinoid in this view, the 

 left side is the right side of an illustration. But in all cases, 

 when we have used the words right side or left side, we have re- 

 ferred to the illustration and not to the disputed question as to 

 which was the right side or the left side of the animal itself. It 

 is no easy task to reform the crinoid literature and reduce it to 

 a uniform, plain system, governed by a simple statement of the 

 facts as they are known to exist, and we have not undertaken it. 



Mr. A. Albers has a specimen of B. argutus, from Burlington, 

 Iowa, that has the arms arranged just as they are in the type, and it 

 has the same form and number of regular iaterradials, but it has seven 

 axygous plates instead of six. The additional azygous plate is a 

 small one in the third range on the left of the azygous area. The 

 fact that this twenty one armed species occurs at Sedalia and at 

 Burlington, is another evidence of the fixity of the species, and 

 of the value of the radial series, within the calyx, in determining 

 the limit of a species. 



In describing B. argutus, we were made to say, that it is the 

 first species bearing twenty-one arms, described from the Burlington 

 Group; but we should have said, it is the second species, for B. 

 rotundus was described many years ago and possesses twenty-one 

 arms. 



The study of animal life has led the most extensive observers 

 and best thinkers to the conclusion that nature is continuous, and 

 the more complete the knowledge of any particular family or 

 genus, the less differentiated are the species, in the mind of the 

 observer, because of the existence of intermediate forms. There 

 are hard lines, however, that separate many species, in the fossil 

 world, and these are found, evidently, among the crinoids. We 



