384 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Fig. 3. — Scales of Gyrodiis coccoderma. 



[June 23, 



Mr. Etheridge having kindly directed my attention to some spe- 

 cimens of Pycnodont teeth deposited in Jermyn Street hy Mr. Man- 

 sel, I found amongst them a fine example of the vomer of a^ 

 Cryrodus (fig. 4), which, from its size, may very possibly have belonged 

 to Gyrodus coccoderma. This conjecture is strengthened by the fact 

 that it was found in the same stratum and in the same locality, 

 viz. in the Kimmeridge Clay of Kimmeridge. The dentigerous area 

 of the bone measures two inches and eight-tenths in length. The 

 breadth at the base is one inch and three-tenths, and at the apex 

 seven-tenths of an inch. It is furnished with five rows of teeth. 

 The median row contains nine large circular tritores, much abraded 

 on the grinding surface. A tenth tooth is wanting at the base. 

 Next in size come the marginal rows. One of these contains 

 fourteen, the other (imperfect) thirteen teeth. They differ in form 

 from those of the median row in having the outer periphery trun- 

 cated, and the outer edges raised. Although somewhat used, they 

 still retain the gyrations characteristic of the genus. The inter- 

 mediate row contains the smallest teeth. There are fourteen in 

 each row, rather irregular in form, but more or less circular. The 

 surfaces are deeply furrowed, as they have suffered little from use. 

 This specimen differs from all the vomerine remains of Gyrodus 

 yet figured ; it approaches more nearly to a species named Pycnodus 

 Butertrei by M. E. Sauvage, from the Portlandian rocks of Portel, 

 which may possibly be a Gyrodus having the teeth much worn; 



