December 14.1k, rpij.] PROCEEDINGS. xxi 



called to the fact that the Hindu god Indra, who was associated 

 with the elephant, killed Vritra, who kept the rain in the clouds, 

 just as the Central American elephant-headed god stood upon 

 the head of the serpent who prevented the rain from reaching 

 the earth. 



Mr. T. A. Coward, F.Z.S., F.E.S. read a paper entitled "A 

 Change in the Habits of the Black-headed Gull." 



This paper is printed in full in the Memoirs. 



Ordinary Meeting, December 14th, 19 15. 



The President, Professor Sydney J. Hickson, M.A., D.Sc, F.R.S., 



in the Chair. 



Mr. F. G. Percival, B.Sc, read a paper entitled "The 

 Punctation of the Brachiopoda." 



The shells of the Terebratulacese are perforated by thousands 

 of little pores, through which pass tube-like processes of the 

 mantle. The number of these puncta per sq. mm. varies in 

 different species, and this variation has been used as a means of 

 distinguishing between different species. 



Unfortunately, an examination of large numbers of individuals 

 belonging to one species shows that the variation within a single 

 species is so great as to render the character useless as a means 

 of distinction ; e.g. 166 individuals of Terebratula biplicata, 

 (Brocchi), were examined and the puncta were found to range 

 from 39 to 129 per sq. mm. Similarly 367 specimens of T. 

 punctata, Sow. showed a total range from 66 to 240 per sq. mm. 

 All the readings were taken at approximately the same distance 

 from the umbo, because the number per sq. mm. increases with 

 the distance from this point. 



These two species alone cover the greater part of the total 

 variation possible for the group, and the variation is therefore 

 almost useless as a means of specific distinction. 



