Blastoidocrinus carcharidens Billings 



Fig. I Photomicrograph xio of a portion of the underside of a 

 wing plate. A small figure of this specimen was given in 

 Bulletin 107, plate 6 at k. The oral end is at the right. 

 The undersurface shows that it was in close contact with 

 the covering plates. In the collection of the State 

 ]\Iuseum 

 2 Photomicrograph xio (through error the enlargement 

 here was very slightly under 10 dia., the correct ratio 

 being' 58 = 6) of a small area of the fragment figured 

 in Bulletin 107, plate 5 at j. The oral end is at the left. 

 a One of the ossicles covering the left side of a food 

 groove. Its boundaries have lost some of their dis- 

 tinctness through the process of reproduction from 

 the photograph but are still recognizable. Back of 

 this left row the tops of several members of the 

 right row are shown. The groove between them car- 

 ried a wing plate like that shown above, 

 b The outer face of one of the adambulacrals. The 

 vertical oval-shaped openings are portions of food- 

 collecting basins that discharged their food through 

 smaller pores opening directly into the food groove. 

 The narrower dark vertical channels leading down 

 from the food-segrating basins were drainage 

 channels for surplus water and discharged into the 

 hydrospires. Views of these channels as seen from 

 above are shown in the three remaining figures from 

 uncovered adambulacra. 

 c Remains of portions of the brachioles which still 

 remain attached to both adambulacra and covering 

 pieces, 

 d The upper edge of a deltoid. This fragment is from 

 Valcour island, Lake Champlain, and belongs to the 

 Carnegie Museum. 

 3-5 Photomicrographs xio of upper surface of portions of the 

 three adambulacra still present in the type specimen. Six 

 covering pieces still remain on the " arm " shown in 

 figure 3. but these are much weathered. The remaining 

 figures show only the upper surface of the adambulacra, 

 the traces of the food groove, the openings into the hydro- 

 spires and the edges of the deltoids. In the Museum of 

 the Geological Survey of Canada 



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