18 



FOSSIL FISHES. 



Batoidei. — Rays. — In Table-cases 32 and 33, are seen a most 

 interesting series of remains of fishes of this family, comprising sets 



of the tessellated palatal teeth of Myliobatis and 

 JEtobatis, from the Eocene Tertiary formation. 

 These " Sea-devils," or " Eagle-Rays," are amongst 

 the largest of living fishes, one taken at Messina 

 weighing as much a3 1250 lbs. ; those met with off 

 Barbadoes being still larger. One captured at 

 Jamaica measured 15 feet in breadth and as much 

 in length, and was four feet in thickness (Gunther). 

 The same case contains specimens of the curious 

 prickles of the " Thornback," JRaia antiqua (Fig. 

 22), from the Norwich Crag, etc. ; and portions 

 of the toothed rostral bone of the "Saw-fish," 

 Pristis, from the Middle Eocene of Bracklesbam, 

 Sussex. 



Fig. 22. — Dermal 

 Spines of the Thorn- 

 back, Raja ctavata. 



Sub-order IT. — Holocephala. 



Chimceroidei. 



The Chimseras resemble the Sharks in many important points of 

 structure. The skeleton is cartilaginous and notochordal, the sheath 

 presenting how r ever numerous calcified rings. The first dorsal fin 

 has a powerful spine attached to its base. The teeth consist of 

 four dental plates above and two below. 



They are represented in Table-cases 33 and 34, by numerous 

 jaws of Elasmodus and JEdaplwdon from the Eocene ; the latter 

 genus also occurs in the G-ault, Greensand, and Chalk; and 

 Iscliyodus from the Gault, Greensand, and Oolite (Table-case 34), 

 and Ganodus from the Great Oolite, Stonesfield. 



There is little doubt that the spines known under the name of 

 Leptaca?ithus, found in the same matrix with Chimseroid jaws, from 

 the Chalk to the Lias, belong to one and the same fish. 



Other remains of Chimssroids may be seen in Wall-case No. 3c. 



Order II. — Ganoidei ?* 

 Sub-order I. — Acanthodini. 



The Acanthodians form an interesting group of very small or 

 moderate-sized Palaeozoic fishes characterized by the presence of 



* We have felt some doubt as to the propriety of placing the Acanthodini, the 

 Placodermata, and the Dipnoi, under the order Ganoidei : from the observations of 

 Prof. Huxley, Dr. R. H. Traquair, and others, it seems quite probable that these 

 ancient types of fishes, when better understood, may hereafter form more than one 

 distinct order. 



