58 



The vault is convex, bears a small central proboscis, and is sub- 

 stantially covered by three circles of large plates. Some of the 

 sutures are anchylosed in the larger circle of plates, and hence 

 they are not shown in the illustration. There are seven plates in 

 the middle circle, and five at the base of the short central pro- 

 boscis that contains the azygous opening. The surface of the 

 plates is de.stroyed, but a node may be seen on each plate over 

 the junction of the ambulacra! canals. There is a small "ovarian 

 aperture" close to each side of each ambulacral opening, which 

 gives to this species thirty-four of these openings. 



This species is readily distinguished from all others by its gen- 

 eral form, surface ornamentation, and seventeen arms. 



Found in the Hamilton Group, at Charlestown, Indiana, and 

 from the collection of Wm. F. E. Gurley. 



Family CAKYOCKINID.53. 

 Family STRIBALOCYSTID.E. (?) 



STRIBALOCYSTITES SPH^BOIDALIS, n. sp. 



Plate V, Fig. 19, anierior side; Fig. 20, basal view, plates injured 



a little ivhere the column attached: Fig. 21, 



summit tnew. 



Body broadly obovate and expanded into an obtuse rim below 

 the summit. Surface of the plates granular, those on the vault 

 convex. Sutures beveled. 



Basals four, of unequal size, and forming an irregularly expanded 

 cup with an hexagonal summit, and slightly re-entering angles at 

 the sutures. Second series of plates expand to the upper third, 

 where they are tumid and abruptly bent over toward the summit, 

 two pentagonal, two hexagonal and two heptagonal. The heptago- 

 nal plates are the larger plates in this .series. There are eight 

 plates in the third series, of unequal size, and not in line by rea- 

 son of curving over the large heptagonal plates in the second 

 series. They are slightly convex and directed toward the summit 

 of the body. Two of them adjoin the mouth which is surrounded 

 by four plates. 



The entire summit i.s covered by seven plats, four of the larger 

 of which occupy the central part of the suuimit, and there is one 

 minute plate on one side of these and two small plates on the 



