FISHES OF THE OLD RED SANDSTONE. 



589 



lected for the illustration of this volume were submitted to his examination, and many 

 of them have already been described in his admirable work (Recherches sur les Pois- 

 sons fossiles). From that work, and from communications addressed directly to my- 

 self, the following descriptions are derived. In them we learn, that as some of these 

 fossils are almost connecting links between crustaceans and fishes, the first rude guess 

 of geologists was after all not remote from the truth, 



FISHES OF THE OLD RED SANDSTONE. 



Cephalaspis, Agass. 



Cephalaspis Lyellii, Agass., PI. 1. f. 1. and PI. 

 2. f. 1, 2 and 3. 



• * rostratus, Agass., PL 2. f. 4 and 5. 



Lewisii, Agass., PL 2. f. 6. 



Lloydii, Agass., PL 2. f. 7, 8 and 9. 



Ctenac anth us, Agass. 

 Ctenacanthus omatus, Agass., PL 2. f. 14. 



Onchus, Agass. 



Onchus arcuatus, Agass., PL 2. f. 10 and 11. 

 semistriatus , Agass., PL 2, f. 12 and 13. 



Cheirolepis, Agass. 



Cheirolepis Traillii, Agass. vol. ii. 1. 1 d and 1 e. 

 f. 4. 



uragusf Agass. vol. ii. t. le. f. 1, 



2 and 3. 



Diplopterus, Agass. 

 Pro. Brit. Ass. vol. iv. p. 75 3 Agass. vol. ii. p. 113, 



Cheiracanthus, Agass. 



Cheiracanthus Murchisonif Agass. vol. ii. 



t. 1 c. f. 3 and 4. 

 minor, Agass. vol. ii. 1. 1 c. f. 5. 



Holoptychus, Agass. 

 Holoptychus Nohilissimus, Agass., PL 2 his. 



Ptychacanthds, Agass. 

 Ptychacanthus? (spine of), PL 1. f. 9 and 10. 



Dipterus, Cuvier. 



Dipterus macrolepidotus, Agass., also Sedgw. 

 and Murch., Geol. Trans., vol. iii. p. 143. 



Osteolepis, Val. and Pent. 



Osteolepis macrolepidotus, Val. and Pent, j 

 Agass. vol. ii. t. 2. f. 1, 2, 3 and 4, and 

 t. 2 c. f, 5 and 6. 



— — microlepidotus, Val. and Pent. ; 



Agass. vol. ii. t. 2 c. f. I, 2, 3 and 4. 



1. Cephalaspis Lyellii, Agass., PI. 1. f. 1. and PI. 2. f. 1,2 and 3. (Recherches, vol. ii. 

 tab. 1 a. figs. 1, 2, 3, 4 and 5 ; and tab, 1 b. figs. 1, 2, 3, 4 and 5.) 



This species, so abundant in the Old Red Sandstone both of England and Scotland, is constituted 

 by M. Agassiz the type of this genus, because the most perfect specimens yet discovered belong to it. 

 The individual represented, PL 1. f. 2. (from the cabinet of Mr. Lyell) presents its dorsal aspect, 

 the head being seen along its superior surface with its lateral prolongations. "This specimen," says 

 M. Agassiz, "is particularly instructive, as it exhibits the junction of the head with the body, the 

 disposition of the scales on the nape (nuque) and the middle of the back, and the points of insertion 

 of the two dorsal fins. (Fig, 1. of the same Plate is also from a specimen in Mr. Lyell's collection.) 



e< The head of this fish is very large in proportion to the body, and occupies nearly one third of its 

 whole length. The outline is rounded, in the form of a crescent, the lateral horns inclining slightly 

 towards each other, while the anterior and central parts project much. These lateral prolonga- 



4 F 



