UmTACEINUS: ITS STEUCTUEE AND EELATIONS. 



73 



development of a given type with a degree of confidence not otherwise 

 attainable. This consideration will, I trust, be a sufficient warrant for my 

 giving an exhibit of the observed facts in this case to an extent that might 

 otherwise appear superfluous. For the purpose, therefore, of showing the 

 extent of the variations in this genus, and of affording means of comparison 

 as to characters already discussed, and also of demonstrating the soundness 

 of the conclusion of Wachsmuth and Springer as to the mode of increase 

 of the supplementary plates, I have collated upon the following table the 

 facts as I have recorded them in about six hundred and fifty specimens ; 

 giving not only the number of interbrachials, but also the character of the 

 base, and some other details. The table includes specimens from the several 

 principal localities, and I have arranged them in the order of their size, 

 beginning with the smallest : — 



TABLE F. 



Variations in Interbrachials and Base. 





Width 

 of 



Number of Plates. 



Form 





Specimen. 







01 



Remarks. 





Calyx. 



iBr. 



illBr. 



Base. 





Loc. 2. LY cc 



6.25 



5- 7- 





D 





K* 1 



6.25 



4- 



1-2- 



D 





LV^ 



7.50 



4- 



— 



M 





" k 



7.50 



4- 







D 





" 



7.50 



5- 







D 





" s 



7.50 



4- 



— 









" aa 



7.50 



5- 







D 





K 26 



7.50 



5- 5- 



2— 



D 





30 



7.50 



5- 5- 













67 



7.50 



5- 5- 













I^V# 



9.00 



4- 5- 



— 



M 





132 



10.00 



5- 6- 



— 









-LYh 



10.00 



5- 5- 



^_ 



D 





'' hb 



10.00 



7- 



— 









K 1 



10.00 



5- 6- 



2- 



D 





146 



11.00 



5- 







D 





LV^ 



11.00 



7- 



__ 









37 



11.00 



8- 



2- 



D 





216 5 



12.00 



4- 5- 



2- 



M 





136 



12.50 



5- 6- 













\Nl 



12.50 



8- 8- 



2- 



D 





" z 



12.50 



6- 







M 



4 basalB. 



" gg 



12.50 



5- 



— 



D 





K 24 



12.50 



5- 5- 







D 





'' 68 



12.50 



5- 5- 







D 





LVIII c 



14.00 



5- 5- 6- 



2- 



D 





K 23 



14.00 



5- 5- 6- 







D 





* Specimens noted " K " belong to the Kansas University ; the others to the writer. 



