PLATE 22. 

 Hyattechinus rarispinus (Hall). Page 292. 



Figs. 1-tS, S. Waverly Group, Lower Carboniferous, Warren, Pennsylvania; collected by the late Professor C. E. Beecher, 



and now in Vale University Museum. 



Fig. 1. Yale Mus. Coll., 332. Natural size. External mold of the ventral side, and m areas B, C, and D in part an internal 

 mold of the dorsal side. Ambulacra petaloid ventrally and narrow dorsally; the interanibulacra all show a primordial 

 interanibulacra! plate in the basicoronal row and a rapid introduction of succeeding columns of plates. Ambulacra! 

 plates only on the peristome. Tubercles are seen on the ventral portion, as that is an external mold: no tubercles 

 on the portion that is dorsal, as that is an internal mold (pp. 21, 22). Drawing, Plate 23, fig. 1. 



Fig. 2. Yale Mus. Coll., 3.33. Counterpart of the same specimen as fig. 1. Internal mold of the ventral side, and in 

 areas A, B, C, and D in part, an external mold of the dorsal side. An impress of the lantern fills the oral area. Draw- 

 ings, Plate 23, figs. 2, 7. 



Fig. 3. Yale Mus. Coll., 329. Natural size. External mold of the ventral side, showing broad petaloid ambulacra, inter- 

 ambulacra with tubercles, and in places spines impressed in the mold. The peristome is covered with ambulacra! 

 plates only. 



Fig. 4. Yale Mus. Coll., 328. Counterpart of the same specimen as fig. 3. External mold of the dorsal side. Ambulacra 

 narrow, interanibulacra with tubercles and a general impression of the dorsal face of the lantern, caused by the flat- 

 tening of the test. 



Fig. 5. On the same slab as fig. 3. Yale Mus. Coll., 329. External mold of the ventral side, showing in part structures 

 as in fig. 3. Drawing, Plate 23, fig. 6. 



Fig. 6. Counterpart of same specimen as fig. 5. Yale Mus. Coll.. 32s. External mold of the dorsal side, showing in 

 part structures as in fig. 4. 



Fig. 7. Waverly Group, Lower Carboniferous, Meadville, Pennsylvania Amer. Mus. Nat. Hist. Coll., 6,392. Holotype. 

 Natural size. External sandstone mold of the dorsal side. Ambulacra narrow, plates low, eleven columns of plates 

 in each interambulacral area (pp. 294, 395). Drawing. Plate 21, fig. (5. 



Pig. 8. Yale Mus. Coll., 325. Natural size. External mold of the dorsal side. Ambulacral areas narrow, interanibulacra 

 with 11 columns of plates in areas A and G, 12 columns of plates in area I, or 13 columns of plates in areas C and E; 

 tubercles prominent; a general impression exists of the top of lantern, caused by the flattening of the test. Drawing. 

 Plate 23, figs. 3, 4. On the reverse side of this slab are more or less complete impressions of seven other specimens 

 of the same species, showing that it was common in the locality. 



