1866.] YOUXG RHIZODUS. 317 



the Chalk, thus also falls to the ground. The absence of this mem- 

 ber cuts oif Eurysomus from the Pycnodonts proper, which are thus 

 restricted to Mesozoic times ; for that family is clearly separated from 

 Eurynotus and Mesolepis by the form of the suprascapular bones, as 

 well as by the different position of the opercular plates, by the 

 structure of the scales, and by the absence of fulcra on the upper 

 caudal lobe. 



EXPLANATION OF PLATES XX. & XXI. 



Plate XX. 



Fig. 1. Amphicentrum gramdosum, one-half the natural size. 



2. Maxilla of A. granulosum, natural size. 



3. Mandible of A. granulosum, seen from without. 



4. The same seen from above. 



5. Outer surface of a scale of A. granulosum, natural size. 



6. Inner surface of a scale of A. granulosum, natural size. 



7. Palatine armature of A. granulosum, magnified. 



Plate XXI. 



Fig. ] a. Mesolepis Wardi, natural size. 



1 b. Outer surface of scales of M. Wardi, magnified. 

 1 c. Inner surface of scales of M. Wardi, magnified. 



2. Head of Platysomus parvulus, twice the natural size. 



3. Teeth of Mesolepis Wardi, twice the natural size. 



5. Note on the Scales of Ehizodus, Owen. 

 By John Young, M.D., F.G.S. 



[This paper was withdrawn by permission of the Council.] 



[Abstract.] 



Attention was drawn to the fact that, on a slab in the collection 

 of the Eoyal Society at Edinburgh, the characteristic Bhizodus teeth 

 occur along with thick bony scales, whose exposed area is orna- 

 mented with coarse tubercles, usually irregularly disposed, while the 

 overlapped anterior area is concentrically striated. These characters 

 confirm the generic distinctness of Wiizodus from Ilolojotychius, 

 whose smooth anterior and rugose free surfaces contrast with those 

 described. 



March 7, 1866. 



Edward Filliter, Esq., Leeds ; Myles Kennedy, Esq., Hill House, 

 Ulverston ; and Lieut. Charles Warren, R.E., Gibraltar, were elected 

 "Fellows. 



Dr. Joseph Leidy of Philadelphia was elected a Foreign Member. 



Prof. J. P. Lesley, of Philadelphia ; and Prof. Eeuss, of Vienna, 

 were elected Foreign Correspondents. 



