PLATE III. 
Fig. _ Page 
1. Diplacanthus longispinus, Ag.; ventro-lateral aspect of 
fish.—L. Old Red Sandstone; Gamrie. a. Anal fin- 
spine. d v d 2 . Dorsal fin-spines, i. Intermediate pair 
of spines, pet. Pectoral fin-spines, plv. Pelvic fin- 
spines. cc. Pectoral arch. [P. 4041.] 27 
2. Squalorajci polyspondyla , Ag.; right mandibular (or left 
palatine) tooth, inner aspect.—L. Lias ; Lyme Regis. 
[43970.] 42 
3. 3 a. Myriaccinthus granulatus, Ag.; left mandibular tooth, 
inner and symphysial aspects.—-Ibid. s. Bevelled sym- 
physial surface. [P. 3099.] 50 
4. Ditto ; dermal plate, outer aspect, twice nat. size.—-Ibid. 
[P. 1158.] 50 
5. Myriaccinthus, sp. (?); dorsal fin-spine.—-Ibid. 
[P. 2850.] 51 
6. Heteracanthus heterogyrus (Ag.) ; fragment of dermal spine, 
lateral aspect, twice nat. size.—Devonian ; Prussia. 
[P. 2248.] 125 
