PLATE IV. 



UlNTACRINUS SOCIALIS. STRUCTURE OF THE VeNTRAL SiDE. 



Fig. 1. Specimen vertically compressed ; showing the black carbonaceous integument 

 studded with irregular calcareous spicules not in contact ; mouth and ambu- 

 lacra in place, and the large anal tube lying flat upon the disk. 



Specimen No. 75. 



(See PL VII., Fig. 1, infra, for enlarged photograph of disk.) 

 " 2. Similar view of another specimen; the disk paved with smaller spicules, the 

 ambulacra in place, and the anal tube curled and crushed upon itself. 



INTo. 71. 



'' 3. Specimen diagonally compressed ; showing part of disk, with ambulacra near the 

 mouth, and the anal tube nearly erect between the arm bases. ISTo. 76. 



^' 4. Specimen laterally compressed, with middle of disk pushed upward and sur- 

 mounted by the anal tube in an erect position. No. 148. 



'^ 5. Specimen laterally crushed ; the disk and anal tube, instead of being pushed 

 upward as in Fig. 4, have fallen inward, and have been caught between the two 

 opposite walls of the calyx when the Crinoid was embedded 5 the anal tube is 

 brought into view by the removal of some plates of the outer wall of the calyx. 

 The black membrane lining the whole calyx is shown at the lower part of the 

 fracture. No. 30. 



(In the last two figures, for greater clearness in drawing, the artist was instructed 

 to leave out of view a confused mass of calyx plates, brachials and pinnules 

 forming the background of the tube. This does not impair the accuracy of the 

 drawing of the structures desired to be shown, as the tube in each case is as 

 plain and well defined in the specimens as here shown.) 



" 6. Actinometra strata P. H. C. View of the disk, showing position of mouth and 

 anus, and distribution of ambulacra. X 2. (After Carpenter.) 

 Figs. 7-9. Actinometra paucicirraBeW. X3; and 



Fig. 10. Actinometra nobilis P. H. C. X 3^. Showing variations in the base of this genus. 

 (After Carpenter.) 

 (All figures not otherwise noted natural size. Figs. 1-5 by Chapman.) 



