250 A. Sarker — Rocks from, the Tonga Islands. 



in future may be known as Sterrholophus flabellatus, Marsh. There 

 is some evidence that other forms, quite distinct, left their remains 

 in essentially the same horizon of the Laramie, but their true 

 relation to the above genera cannot be settled without further 

 discoveries. 



This group so far as at present investigated is very distinct from 

 all other known Dinosaurs, and whether it should be regarded as a 

 family, CeratnpsidcB, as first described by the writer, or as a sub- 

 order, Geratopsia, as later defined by him, will depend upon the 

 interpretation and value of the peculiar characters manifested in its 

 typical forms. 



The main characters which separate the group from all other 

 known families of the Dinosauria are as follows : 



(1) A rostral bone, forming a sharp, cutting beak. 



(2) The skull surmounted by massive horn-cores. 



(3) The expanded parietal crest, with its marginal armature. 



(4) A pineal foramen. 



(5) The teeth with two distinct roots. 



(6) The anterior cervical vertebree coossified with each other. 



(7) The dorsal vertebrse supporting, on the diapophysis, both 

 the head and tubercle of the rib. 



(8) The lumbar vertebrse wanting. 



The animals of this group were all herbivorous, and their food 

 was probably the soft succulent vegetation that flourished during 

 the Cretaceous period. The remains here figured are from the 

 Ceratops beds of the Laramie, and were found by Mr. J. B. Hatcher, 

 in Wyoming, on the eastern slope of the Rocky Mountains. 



IIL — Notes on a Collection op Eocks fkom the Tonga 



Islands. 



By Alfked Harkbr, M.A., F.G.S., 



Fellow of St. John's College, Cambridge. 



THE Tonga or Friendly Islands in the South Pacific Ocean seem 

 to have received hitherto no attention from geologists, and 

 I can find no published information as to their geological constitu- 

 tion beyond the simple record of the existence of volcanoes and 

 coral-reefs. The material of these brief notes was mostly collected 

 by Mr. J. J. Lister, M.A., during the cruise of H.M.S. Egeria in 

 3889; and, through the courtesy of Captain Wharton, E.N., F.R.S., 

 Hydrographer to the Admiralty, I have had the opportunity of 

 examining a few additional specimens collected by Captain C. F. 

 Oldham, E.N., Commander of the Egeria, in 1890. In view of the 

 general account of the islands which IVIr. Lister is preparing, I notice 

 here only such points as arise directly from an examination of the 

 specimens. 



It is well known that most of the Pacific Islands which have been 

 explored seem to be built largely of either volcanic or calcareous 

 formations, usually supposed to loe of Eecent origin. Indeed the 

 idea seems to have been entertained in some quarters that such was 



