INDIANA PALEONTOLOGY. 8i. 



Fig. 17, plate 27, is an elongate specimen, almost circular in cross section, 

 the anal plate arising but little above the general surface. The summit plates 

 have been removed by weathering, and five little pits with sharp division walls 

 (sutures) indicate their former presence. The spiracles and usual opening 

 also show well on this specimen. 



Figs. 18 and 19, plate 27, is an elongate specimen with but four ambu- 

 lacra, the place of the fifth being represented by a line only. The base, how- 

 ever, is quite regular in outline. The central summit opening is closed by four 

 large plates and a double series of smaller plates extend outward for a little 

 distance over the ambulacra. 



Fig. 20, plate 27. In this specimen the anal plate is boundsd on either 

 side by an extra, elongate, triangular plate, shorter on the left side, the whole 

 forming an irregular protuberance above. Thus we have in this specimen, 

 three anal plates. The central summit opening in Fig. 20 is closed by a roof 

 •of small plates. 



Fig. 21. plate 27, is a basal view of a very elongated specimen, showing a 

 beautifully preserved basal cavity with the top stem joint and its minute cen- 

 tral perforation. 



The outer sutures of the basal plates show in the pit, but could not be 

 reproduced in the drawing. 



The ornamentation of the radial and interradial plates is beautifully pre- 

 served in the specimen, and the folding of the radials about the lower ends of 

 the ambulacra, form five little foot like projections. 



Fig. 22, plate 27, is a side view of a plump specimen, in wiiich again the 

 anal plate is burdened on either side by what seems to be elongate triangular 

 plates, but unlike figure 20, in that the triangles have their acute angles above, 

 and their broadest part below. It is nearly inipossi])le to determine, from the 

 silicified character of the specimen, whether these are real plates or folds. 



Fig. 23, plate 27, is a summit view of a specimen, in which the ven- 

 tral surface is covered by a roof of granular plates, and the spade like ends of 

 the interradials concave and granular. 



In this specimen the anal plate is considerably elevated above the surface, 

 near the summit, and the bounding edges of the interradials form elevated 

 rims about the spiracles. 



The base of this specimen is clean, and shows the sutures of the basal 

 plates, and the anal plate is bounded, either side, by an apparent elongated 

 triangular plate as in figure 22. 



Horizon, locality and collection same as the last. 



