PLATE XXII. 



TAGE. 



Wig. 1-5. Erismacantiius McCorANUs; St J- and W 46L 



la. Side view of nearly entire spine, enlarged two diameters; I b, c d, enlargement of 

 tubercles from various parts of the anterior prong. St. Louis limestone; St. 

 Lonis, Missonri. 

 -2 a. Side view of an imperfect worn specimen, exhibiting perfect transverse sections of 

 either prong, as shown in tig 2 b, c. d. Same horizon, A; ton, Illinois. 

 ■3<i- Left side of posterior prong, enlarged two diameters, showing cos ration ami den ticti: 

 late posterior border; -i b. anteiior border, folded longitudinally as though by 

 pressure; 3 c enlargement of posterior border, showing form and arrangement 

 of denticles, etc.; :l d, enlargement of two denticles, seen from above. Same 

 horizon and locality. 

 4 a. Side view of posterior spine, enlarged one-half showing more widely spaced denti- 

 cles of posterior border, and tuberculatum of anterior intercostal space; 4 b, 

 transverse section, compressed, ami. 4 c. restored outline; 4 d, sideand view from 

 above of one of the posterior denticles. Same horizon, St. Louis, Missouri. 

 5*. Section from a large anterior spine, enlarged two diameters, showing crowded 

 arrangement of tubercles in some specimens- Same horizon and locality. 



Fig. 6. Am acanthus gibbosus, (N and W. sp ) 4G4 



6 a. Side view of a nearly perfect spine, enlarged one-half; f> 6. enlargement of section 

 near the middle of the- spine, showing bifurcated ad interpolated costa?, denti- 

 culation of anterior and posterior- binders; fie, transverse section, enlarged. The 

 original specimen of Uomacanthus gibbosus, Vol. II, PI. XII, f. 1. St. Louis 

 limestone; St. Louis, Missouri 



fig. 7-9. Marracanthus RECTUS {X and W. sp ) 466 



la. Side view of perfect spine, enlarged two diameters; 7 &, enlargement of portion of 

 extremity; 7 c. similar enlargement of section from lower part of spine, showing 

 lateral face; 7 d, similar enlargement of a seciion shewing the posterior face; 

 7 e,f, g, h i, enlargements showing different views of the, large anterior denticles 

 . neaYthe summit of the spine; 7 k, transverse section, enlarged. St Louis lime- 

 stone; St. Louis. Missouri 

 &a. Sketch of a small spine, showing the anterior aspect, and laterally expanded flattened 

 base ; 6 b, lateral view, outline ; 8 c, transverse section across the inserted base. 

 Same horizon and locality. 

 9 a- View of a fragment of a large spine, showing portion of the posterior face, the cen- 

 tral cavity and posterior face of the expanded base ; 9 b, c, d, traus verse sections 

 at points indicated by corresponding letters in preceding figure. Same horizon 

 and locality. 



Fig. 10,11. Lecracanttks lxguiculus, St J and W 476 



10«. Side view of a medium-sized, nearly perfect spine, enlarged two diameters; 10 b, en- 

 largement of tubercles from near lb*; middle of the spine ; 10 c. transverse sec- 

 tions near middle and across the transversely expanded base, the upper side 

 being the posterior or concave border, enlarged two diameters. St. Louis lime- 

 stone ; St Louis, Missouri. 

 41a. Lateral view of a fragment showing the upper extremity of a large specimen, en- 

 larged two diameters; \\ b, transverse section of one of the large apical denti- 

 cles; 11 c enh eioentof tubercles; II d, transverse section across the posterior 

 prom in tfc - edge corresponding to the posterior margin. Same hori- 



zon and locality . 



