'384 Proceeding* of the British Association. 



tenor, however, about a mile south of the Causeway headlands, 

 the chalk seems to continue its course straight west in an un- 

 broken line, till it re-appears near the mouth of the Bush River. 

 In fact the Causeway seems to be merely part of a great ridge 

 or outburst of columnar trap, which runs E. and W. along the 

 north coast, and includes the Fair head, the southern promon- 

 tory of Rathliiij the various islands, and some parts of the coast 

 about Ballintoy, the Causeway itself, and the rocky isles adja- 

 cent, and finally the Skerries and Ram ore Head at Portrush. 

 In its whole course it seems to cut off the upper secondary rocks, 

 and at Portrush to have been infused beneath the lias clay form- 

 ing the altered basaltiform fossiliferous rock at that place, whose 

 nature has been so much controverted. 



7. Professor Phillips communicated the results of his inves- 

 tigations regarding the Geological distribution of Belemnites. 

 He observed that no less than one hundred species were now 

 known, and of these about thirty -four species had been found 

 in England. Shells of this genus are confined to the chalk, 

 oolite, and lias, and the results which their study affords con- 

 trasts remarkably with the negative indications deduced from an 

 examination of the fossil Astaci. One division, characterized by 

 a slight swelling at the apex, and possessing a lateral fissure, 

 was confined to the chalk. The species, which were obtusely 

 mucronate, are found in the green-sand. The species with a 

 groove on the back are found in the middle oolite ; those with 

 a lateral groove in the lias and lower oolite ; and those species 

 which are destitute of a groove are confined to the lias. From 

 these remarks, it appears that not only are the species of Belem- 

 nite confined to certain strata, but that even certain natural di- 

 visions of the genus are found together in the same beds, and in 

 no others. Another interesting remark is, that species which 

 are common in the chalk of the Continent, are rare in the chalk 

 of England, and vice versa. M. Agassiz communicated some 

 interesting observations on the organization of Belemnites, and 

 on their relations to recent Cephalopodes. By a careful examina- 

 tion of a specimen in the collection of Miss Philpot, at Lyme 

 Regis, M. Agassiz has convinced himself that the conical body 

 generally termed belemnite, is the termination of the horny plates 

 frequently found at the same locality with the ink bags, and 



