Description of Plates. 



Piatt 3. 



Figures 1- 5. — Various views of the supposed chorda! sheath referred to Dictyo- 



rhabdus priscus, n. gen., n. sp. 

 Figures 6-14. — Dermal plates of Astraspis desiderata, n. sp. 



Piatt 4- 



Figures 1- 4. — Outer surface of partially ahraded plates referred to Astraspis desid- 



• rata, n. sp. 

 Figures 5-11. — Various views of dermal scales referred to Eriptychius americanus, 



n. sp. It may be that several species are represented. 



Piatt 5. 



Greatly enlarged drawings to illustratt Dr. Otto JaeJceVs remarks on tin microscopic char- 



ii, -i, r& of 'In fossils. | 



Figure 1. — < Toss-section through a plate with haversian canals [V), osteoblasts {0), 



and dentine tubercles /' . 

 Figurt 2. — Two dentine tubercles enlarged to 70 diameters. 

 FigureS. — Oblique section of dentin* tubercle. 

 Figurt 4.— Enlargement to 350 diameters to show osteoplasts [O). The margin is 



shown at a, a, and the rock at /.'. R. 



(172) 



