12 MARSHALL: ON A PARASITE OF LIMN^A TRUNCATULA. 



water, but let them not have access to the ponds and ditches, 

 and so you will arrest what in certain quarters is a veritable 

 plague. Thus can curious biological research give aid amid 

 the difficulties of daily life. 



Mr. Thomas, of Balliol College, Oxford (assistant to the 

 late Professor Rolleston), has gained the deserved merit of 

 unravelling this mystery, and cleared up points impenetrable 

 even to the ingenuity and industry of Leuckhart, who indepen- 

 dently and almost simultaneously made the discovery of the 

 host-ship of Lhnncea trtincahda ; but whereas Leuckhart was 

 uncertain as to his conclusion, later in point of time, and missed 

 the very salient point as to the encystment on the grass (thinking 

 the sheep accidently swallowed the little snails with the contained 

 cercance), there can be no doubt the chief honour will rest with 

 Mr. Thomas, who has devoted two years to this investigation, 

 which, instituted by the late Professor Rolleston at the request 

 of the Royal Agricultural Society, was entirely worked out in 

 the Oxford Museum. And the development of this mystery is 

 an answer to those unphilosophical minds who think naturalists' 

 studies trivial and unimportant. 



Pupa secale var. alba. — It will be as well to correct a 

 mistake in Mr. Rimmer's Land and Freshwater Shells of the 

 British Isles, 1880, wherein, at p. 152, he gives as a locality for 

 this variety "Pateley Bridge, Yorkshire (Lister Peace), y^. C" 

 If the reader will turn to p. 36 of the first volume of the Journal 

 of Conchology, he will see that the shell which Mr. Peace found 

 at Pateley Bridge was Pupa umbilicata var. alba. No doubt the 

 mistake was made through inadvertence, as at p. 155 Mr. 

 Rimmer gives the record correctly under P. umbilicata. From 

 the point of view of the geographical conchologist it is desirable 

 to at once correct a mistake of this kind. — Wm. Denison 

 Roebuck. 



J.C, iv., January, 1883 



