EXPLANATION OF J'IaTHS •27^27*'. 45 



Plate 27^ V.I. p. 281. 



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 Stones- 

 field, Oxon. (Original.) 



Plate 27 ^ V. I. p. 287, Note. 



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



Fig. I. 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, shewing the tubular struc- 

 ture of the bony base. b. Punctate surface of the 

 superficial 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 without 

 enamel, a'. U, 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 tuburculated 

 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-fami- 

 lies of Sharks. (B. \. to B. 13. Agassiz.) 



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

 Cestracionts. See V. I. p. 287. 



