INDIANA PALEONTOLOGY'. 122. 



extra plat« pushed into a ridge and forming a spine-like process between the 

 distal ends of two ambulacra. FroTn the ambulacral tips to the base of the col- 

 umn, the specimen is normal. This inter-ambulacral plate is a sixth fork piece, 

 having an indistinct rounded longitudinal prominence down its center instead 

 of an ambulacrum. Above this inserted radial is but one deltoid, being scarcely 

 wider than the other four but not quito so concave. 



This specimen is from the Kaskaskia group, of Breckinridge county. Ken- 

 tucky. 



Figures 23 and 24 are side and summit views of two internal casts of 

 P. god lit. 



The longitudinal slender ridges on either side of a broader ridge are the 

 casts of the hydrospire sacks, the broader ridge being a cast of the open space 

 just beneath the lancet plate and formed by the median hydrospire folds. 



Notice the great similarity between the ventral view of this cast of Pentre- 

 mites and a like view of the test of a Codaster. The resemblance is striking, 

 the ditference being mainly in the greater number of the slits in an ambulacral 

 field of the latter. Breaks in the fields of the specimens before us show the 

 depths of the folds. 



The same and other features may be seen in the natural casts of the visceral 

 ■cavity ot Sch isoblastus snii'' and Orb'/treniites noi'ujctodl. 



These two specimens (Figs. 23 and 24) are from the Kaskaskia group of 

 Kentucky, and the property of G. K. Greene. 



Figure 25 is a side view of a specimen from which two ambulacra and the 

 inter-ambulacral plates have been removed, showing the cast of the visceral cav- 

 ity. Along the edges of ihe fork and deltoid pieces may be seen the pores that 

 -communicate with the hydrospires beneath. The relative thickness of the 

 ■various parts of the test is also shown. 



From the Kaskaskia group, of Bowling Green, Ky. 



P EN TRE MITES GODONI. l)e France, Rowlev. 



Plate 36. Fros. 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36. 



Figure 26 is a view of the inner surface of a fragment showing two groups 

 of hydrospires. As is usual in this species there are eight tubes to the group. 



The shape of a series is in a general way like that of the ambulacrum, 

 broadest at the top of the fork pieces. The tip is received below into a pocket 

 so that the full length is not seen in the illustration. The relative thickness 

 of the test is also exhibited. 



Figure 27 is a side view of a specimen, preserving the pinules in the left 

 half of one ambulacrum, the right half of the same and parts of two other am- 



