Correspondence — L. M. Parsons. 559 



respectively— 5, 6-J-; 8, 9; 8^, 6^; 6, 6; 3+, 3i ; 6^, 7-^; 21i, 12i- 

 8, 6; 81, 7; 10, 8; lOi-, 10; 7i 6*. 



CO^tl^ESIE'OISrXDEilSrOE. 



THE HOEIZON OF PRODUCTUS HUMEROSUS. 



Sir, — In reply to Dr. AVheelton Hind's letter in the October 

 number of the Geological Magazine, may I point out that there 

 appear to be two forms of Productiis humerosus occurring at different 

 horizons. The earlier form is evidently characteristic of the 

 Belgian " sub-l(sv{s" level (C-S), while the later mutation is found 

 in the Dihunophyllum zone. The late Dr. Yaughan, in his paper on 

 the "Correlation of Dinantian and Avonian ", published in tlie 

 Q.J.G.S., vol. Ixxi, No. 281, refers to this matter, and mentions, on 

 p. 47, that the Clitheroe form is the early variety of Productus 

 suhl(Bvis. For the present I conclude, from evidence stated in my 

 paper, that the Leicestershire beds contain the later advanced form 

 of P. humerosus, and are of Dj age, but I am looking forward to 

 reading, with much pleasure. Dr. Hind's forthcoming paper on the 

 Clitheroe area, and will then carefully reconsider the question. 



* L. M. Paesons. 



110 Lewin Eoad, 



Streatham, S.W, 16. 



OBIT"Cr.A_I?,"2". 



SAMUEL WENDELL WILLISTON, M.D. 

 Born July 10, 1852. Died October, 1918. 



Vertebrate palaeontology loses a distinguished student by the death 

 of Professor S. W. Willistou. After leaving school he entered the 

 Kansas Agricultural College, where his interest in geology was 

 roused by Professor B. F. Mudge. He was then employed by 

 Professor 0. C. Marsh as one of his fossil-collectors in Kansas and 

 other western territories of the United States. At the same time 

 he helped with the preparation of the fossils in the Yale University 

 Museum, and also pursued medical studies, which eventually led to 

 his graduating as M.D. He was deeply interested both in the fossils 

 and in the living animals which he met with during his explorations, 

 and so early as 1877 he began to publish small notes. Professor 

 Marsh, however, discouraged Williston's researches on fossils, and 

 he therefore turned in earnest to dipterous insects, on which he 

 became one of the leading authorities in the United States. In the 

 early eighties he was appointed Professor of Geology and Paleon- 

 tology in the State University of Kansas at Lawrence, where he 

 brought together a great collection of fossils from the Cretaceous 

 and Carboniferous formations of the State. In 1902 he removed to 

 the newly instituted chair of Palaeontology in the University of 

 Chicago, where he continued active researches until nearly tlie time 

 of his death. 



