EXPLANATION OF PLATES 27 c . 27 d . 45 



Plate 27 c .' Vol I. p. 214. 



Fig. 1. Fossil fish of the genus Microdon, in the family 

 Pycnodonts. (Agassiz, Vol. I. Tab. G. fig. 3.) 



Fig. 2. Os Vomer of Gyrodus umbilicatus, from the Great 

 Oolite of Durrheim, in Baden. (Agassiz.) 



Fig. 3. Os Vomer of Pycnodus trigonus, from Stonesfield, 

 Oxon. (Original.) 



Plate 27 d . V. I. p. 21 S, Note. 



A. Teeth of a recent Shark, allied to fossil species. 



Fig. 1. Anterior and Palatal Teeth of the Port Jackson 

 Shark, (Cestracion Phillippi.) (Phillip.) 



Fig. 2. Anterior cutting teeth of Port Jackson Shark, in 

 the College of Surgeons, London. (Owen.) 



Fig. 3. Flat tessellated tooth of the same. Nat. size. a. 

 Outer articular facet, showing the tubular structure 

 of the bony base. b. Punctate surface of the super- 

 ficial enamel. (Owen.) 



Fig. 4. Mesial, and inner articular facet of another large 

 tooth of the same. a. Upper concave margin thinly 

 covered with enamel, b. Lower bony margin with- 

 out enamel, a', b'. Bony base of the tooth exposed 

 by removal of the Enamel. The surface is areolar, 

 from the bending and blending together of the bony 

 tubes, c. c'. Fractured edge of the marginal and 

 superficial enamel. (Owen.) 



Fig. 5. Another anterior cutting tooth, a. Smooth ena- 

 melled point, b. Minutely rugous and tuberculated 

 base. In some of the cutting teeth both sides of the 

 base are rugous. (Owen.) 



B. Various forms of fossil Teeth, in the three sub-families 



of Sharks. (B. 1. to B. 13. Agassiz.) 

 Figs. 1 — 5. Teeth of fossil Sharks in the sub-family of 

 Cestracionts. See V. I. p. 218. 



