Geological Society. 341 



Polystoma loletiformis^ simplex, elongata, lohata, contorta, 

 irregularis, amhigua, &c., Court. Ep. xii. 5, 6, xiii. & xiv. 

 Senonian. 



MetAj Pom. 

 (lb. p. 188.) 



Sponge cylindrical, clavate or nearly globular. Oscula 

 scattered in the vertex. Miocene, Oran. 



Maeisca, Pom. 

 (lb. p. 192.) 

 Sponge from pyriform to globular, with a radiated pit in the 

 vertex, into which a bundle of fine excurrent tubes opens. 

 Surface with scattered large pores. Miocene, Oran. 



[To be continued.] 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



June 5th, 1878.— John Evans, Esq., D.C.L., F.R.S., Vice-President, 

 in the Chair. 



The following communications were read : — 



1. " On the Affinities of the Mosasauridse, Gervais, as exemphfied 

 in the Bony Structure of the Fore Fin." By Prof. Owen, C.B., F.R.S., 

 F.G.S., &c. 



In this paper the author commenced by discussing the opinions 

 expressed by difterent anatomists as to the indications of relation- 

 ship furnished by the structure of the fore limb, and stated that in 

 1851 he had referred Mosasaurus to a tribe Natantia, of the order 

 Lacertilia. Since then Prof. 0. C. Marsh has published a recon- 

 struction of the fore limb of the Mosasauroid Lestosaurus simus ; and 

 from a comparison of his figure with the bones of the same parts in 

 Cetacea, Plesiosauria, and Lacertilia, the author showed that the 

 resemblance in structure was closest with the last-named type, of 

 which the fore foot of Monitor niloticus was taken for comparison. 

 In the relative length of the digits and the number and form of the 

 j)halanges the Mosasauroid fore foot was shown to agree most nearly 

 with the Lacertilian type. With regard to the presence of a zygo- 

 sphene and zygantrum in vertebrae of Clidastes, cited by Prof. Cope in 

 favour of his approximation of the Mosasaurs to the Ophidia and his 

 establishment of the order Pythonomorpha, the author remarked 

 that the trunk-vertebra) of the Iguanidae show zygosphene and 

 zygantrum, but with modifications which serve to distinguish the 



