72 



UINTACEINUS: ITS STRUCTURE AND RELATIONS. 



TABLE E. 







Brachials. 



Number of Plates. 



Specimen. 



Width of 

 Calyx. 





















Length. 



Width. 



IBr areas. 



inBr areas. 



1 



8 mm. 



.75 



1.25 



1- 1- 1 



0-0-0 



9 



10 " 



.75 



1.75 



1- 1- 1 



0-0-0 



3 



10 '^ 



.75 



1.50 



1- 1- 1- 2 



0-0-0 



4 



10 " 



.75 



1.25 



1- 1- 1- 1 



0-0-0 



5 



10 " 



.75 



1.25 



1- 1- 2 



0-0-0 



6 



12 " 



.90 



2.00 



3-4 



0-0-0 



7 



18 " 



1.00 



2.25 



2- 3- 3- 4- 7 



0-1-0 



8 



25 " 



1.00 



2.50 



4_ 3- 4- 4 



1-1-0-1 



9 



25 " 



1.12 



2.75 



5_ 3- 4- 3- 4 



l_l_0-l-0 



10 



30 " 



1.00 



3.00 



5- 5- 4- 3 



1-2-1-1 



U 



31 " 



1.40 



3.75 



4- 3- 3- 3 



1-1-1-1 



12 



35 " 



1.50 



4.25 



6- 5- 5- 4 



3-1-1-2 



13 



35 " 



1.25 



3.25 



12-10- 8-11 



5-4-3-4-4 



14 



37 " 



1.30 



4.00 



8- 6- 7- 6 



4-1-2-2 



15 



37 " 



1.25 



3.75 



12-12-12-15 



3 4 5 7 5 



16 



40 " 



1.50 



4.50 



4_ 6- 8- 6 



4-1-2-2 



17 



40 " 



1.30 



4.00 



15-16-12-13-23 



4-5-4-4 



18 



44 " 



1.30 



4.25 



14_14_14-17-15 



8-6-5-4-5 



19 



50 " 



1.30 



4.50 



15-12-16-15 



4-6-6-7-5 



20 



55 " 



1.50 



4.50 



15-10-17-16 



4-6-6-7-6 



21 



55 " 



1.75 



4.50 



15-16-12-16 



5-6-4-3-5 



Variations in size of brachials and number of interbrachials among twenty-one specimens of 

 Forbesiocri?2us " of various sizes. 



Although the conchision above stated has been generally accepted by 

 other authors, a demonstration of it by direct evidence has not heretofore 

 been given. It is rare, in studying fossils, that an opportunity is presented 

 for comparison of facts in a series of specimens of such extent and variety 

 as is found in the collection of Uintacrinus before me in this investigation. 

 With single specimens, or only a few of them, one cannot always be sure 

 that the characters presented truly represent the species or genus as it is 

 actually limited in nature. Indeed we may be totally misled in our esti- 

 mate of its real character by something that is a mere individual peculi- 

 arity, e. g. PI. YI., Fig. 5, on which, standing alone, we would say without 

 question that the genus had an anal plate. This is especially true of 

 Crinoids of the higher developed types, like the Camerata or Flexibilia, 

 by reason of the complexity of their structure. 



With a large series of specimens, however, the liability to error of this 

 kind is much reduced, and by aggregating the facts thus presented it 

 becomes possible to ascertain the rules that prevail in the structure and 



