26 THE MOLLUSCA OF DORSETSHIRE. 
Sturminster Marshall, J. C. J2-P. 
Swanage, stream; Blashenwell meadows, J. H. Austen ; 
Wareham, Stoborough meadows, J. C. M.-P. 
Physa fontinalis, in common with other water mollusca, 
as Limnea glutinosa, L. stagnalis, and Bythinia tentaculata, 
have the power of thread-spinning for suspension. 
Montagu, at the beginning of the century, noticed this 
habit. He says: ‘‘ Physa (Bulla) fontinalis has a very con- 
siderable locomotive power, and transports itself by adhering 
to the surface of the water, with its shell downward, 
against which it crawls with as much apparent ease as on 
a solid body, and will sometimes let itself down gradually 
by a thread affixed to the surface of the water.” 
APLEXA, Fleming, 1828. 
92. A. hypnorum (Z.) Physa hypnorum (L.) Bulla 
hypnorum L. 
Pulteney, p. 43, pl. 18, f. 20. Purbeck Papers, Vol. ii., p. 46. 
Robinson’s Purbeck, p. 178. 
Upon aquatic plants, in ponds, ditches, wet splashy places 
which are dry in summer. 
Weymouth, Damon; Kast Burton, ditches, Kendall. 
Langton Matravers ; Wilkes Wood, R. H. Soden Smith. 
Swanage, stream ; water-course, Blashenwell, J. H. Austen, 
Wareham, water-courses ; Stoborough Meadows, J. C. IL-P. 
Chamberlaynes, Bere Regis, water-courses, J. C. M.-P. 
Mr. Sheriff Tye, speaking of Aplexa (Physa) hypnorum, says : 
‘* In one case I saw three of these and a Limnea glabra 
upon the thread of one of the former at one time. Often 
when the two Physe met on the same thread they fought 
only as mollusca of this genus can, and the manceuvres they 
went through upon this fairy ladder outdid any that the 
cleverest gymnast could perform. I once saw one 
ascending, and when it was overtaken by another then 
came the tug-of-war ; each tried to shake the other off by 
repeated blows and jerks of its shell and body in a most 
excited manner. Neither being able to gain the mastery, 
one began to descend, followed by the other, which it 
overtook and reached the bottom first.”’—Quarterly Journal 
of Conchology, November, 1878. 
