62 SMITHSONIAN INSTITUTION 



PLATE XXVIII 

 (All figures natural size except where otherwise stated) 



PAGE 



Figs. 1-19. Forbeslocrinus multibrachiatus Lyon and Casseday 255 



(Also on PI. XXIX) 



Fig. 10. The type, laterally compressed; anterior view. The specimen is somewhat weathered, 

 which along with the compressed condition gives the arms a flatter appearance than is 

 seen in numerous well-preserved specimens from the same locality. Author's col- 

 lection. 

 lb. Posterior view of same. The compression has forced the left posterior ray partly over 

 the anal plates, so that some of them are not seen. 



2. Very mature specimen, laterally compressed, posterior view; with stem very well pre- 



served, and arms to the fifth division. Shows anal and interbrachial plates, and the 

 rounded character of the arms. 



3. Posterior view of a similar, but smaller, specimen ; the crown is less flattened, but the 



stem is flattened distally, so that the normal taper is not preserved. 



4. S, 6. Similar flattened specimens with profuse development of anal and interbrachial plates ; 



showing tendency to form vertical series up the middle of anal area. Of the type 

 figured by Meek and Worthen as F. wortheni, Geol. Rep. 111., pi. 4, fig. 2; 12, fig. 7. 



~a, 8a, 9, 10. Smaller specimens in various positions, showing" diminishing number of inter- 

 brachials. 



yb,8b. Ana! areas of corresponding specimens. 



II, 12, 13, 14. Smaller specimens in difi^erent views, showing still further diminution in number 

 of interbrachials. 



14a. Anal area of 14. 



iSa, 16, 17, 180. Still younger individuals, with interbrachials reduced to very few. 



156, i6a. Anal areas of the corresponding specimens; 156, X 2. 



18b. Posterior view, enlarged, of specimen figured at 1817, showing the sutural attachment of 

 anal plates to posterior basal and adjacent brachials. X 2. 



The above mentioned specimens from 2 to 18, all from the same locality and horizon, 

 and belonging to a single colony, form an interesting series showing the development 

 of the interbrachial system with growth of the individual, from very young like 14, 

 IS, 16, with one to three plates, to mature forms like 2, with nineteen or twenty inter- 

 brachials. 



19. Stem with IBB fused ; drawn with small plate at right upper corner, instead of lower as 

 usual. 



Keokuk Gr. ; Lower Carboniferous. Indian Creek, Indiana. 

 All the specimens are in the author's collection. 



