112 HULL SCIENTIFIC AND FIELD NATURALISTS CLUB. 



of this district are very rich in salt, so much so, that some 

 sanguine people have proposed to mine for it as in Cheshire, 

 but have so far met with little encouragement from the East 

 Yorkshire landed proprietor, and also that prior to the 

 cutting of the Market Weighton Canal, over a century ago, 

 the country consisted of saline marshes to which the tide 

 had frequent access. Still the fact that I find it associated 

 with such freshwater forms as Cymatopleura Solea, Gompho- 

 nema acuminatum, and Vanheurckia vulgaris ; and that there 

 are no purely brackish water forms in the same gathering 



Suiirtlla medulica. 



— unless Navicula Integra can be regarded as such — renders 

 its survival under present conditious for so long a time an 

 interesting puzzle. 



A small percentage of the frustules shows a curious dis- 

 tortion caused by an indentation on one side of the valve, 

 as shown in the lower figure. Peragallo's plates show 

 similarly distorted forms of Surirella labelled as distinct 

 species, S. reniformis Grun. being a distortion of S. gemma 

 Ehr., and -S'. Neumeyeri Jan. of S. fustuosu Ehr. 



I am indebted for the drawings for the accompanying 

 plate to the able pencil of Mr. T. Stainforth. 



