116 
SIDNEY F. HARM Eli. 
been registered in the British Museum collection as 
13. 7. 10. 1-2. 
Since the publication of the original description, P. oval is 
appears never to have been rediscovered (cf. Selys- 
Longchamps, 1907, p. 188) ; and it has been supposed that 
the species had been founded on the immature condition of 
some other species. I am happy to be able to confirm the 
accuracy of Strethill Wright’s account; and to show, by 
the occurrence of well-developed ovaries and testes, that it 
must be regarded as an adult form, in spite of its minute size- 
and the small number of its tentacles. The examination of 
the Northumberland material has furnished some explanation 
of the fact that this interesting species has so long escaped 
notice. Although present in very large numbers in the 
material under consideration, it is so completely concealed in 
the substance of the shell that its presence would not have 
been suspected unless the shell had been decalcified. Although 
I have not obtained other specimens, there seems every reason 
to think that the species will be discovered in equal abundance 
when shells of Neptunea or other Molluscs from the north- 
east coast of England and the east coast of Scotland are 
examined by the method of decalcification. 
A further result of the present investigation has been to 
demonstrate the occurrence of a remarkably active process 
of reproduction by fission, in confirmation of the results of 
certain other observers, for other species ; though taking 
place with far greater frequency than is indicated by anything 
that has previously been published. 
The genus Ph or on is was established by T. Strethill 
Wright in a paper communicated to the Royal Physical 
Society of Edinburgh on April 23rd, 1856, and published in- 
two Edinburgh journals (1856 1 , 1856 2 ). Two species were 
distinguished — P. hippocrepia, the tubes of which wer& 
embedded in a stone obtained at Ilfracombe; and P. ovalis,. 
found in a decayed oyster-shell, inhabited also by Cliona 
celata, dredged near Inchkeith in the Firth of Forth. 
Of P. hippocrepia an excellent description is given, so far 
