﻿1874.] G. and H. Nevill — On New Marine Molhisca. 21 



2. The branch lying opposite the line should be 

 equal to the 6th part of the measured conductor resis- 

 tance of the line, and in this, the smallest of all the 

 branches, readjustment of balance should be made 

 only. 



Nos. 1 and 2 necessitate the alteration of all the branches if L, the 

 measured conductor resistance, alters within wide limits. A determination 

 of L will therefore be required from time to time. 



From the development of these general results it will be evident that 

 they fulfil the following conditions : 



I. The irregularitii of signals in the one station is entirely indepen- 

 dent of the irregularity of signals in the other station. 



II. The irregularity of signals in each station is due only to balance 

 not being rigidly established. 



Ill If balance in either station is disturbed, a single adjustment in 

 the branch b will re-establish that balance. 



IV. Any disftcrbance of balance will have the least possible effect on 

 the received signals. 



V. Maximum current at balance. 



VI Maximicm magnetic effect of the maximum current on the receiv- 

 ing instrument. 



(To be continued.') 



Desceiptions of new Maeine Molltjsca peom the Indian Ocean, 

 by Messes. G. and H. Neyill. 



[Received and read 4th March, 1874.] 

 [With Plate I.] 



The present paper is a continuation of two which were published in 

 Vol. XXXVIII for 1869 of the Society's Journal, at pp. 65 and 175. The 

 types of all the species now described are in the extensive collection belong- 

 ing to the Trustees of the Indian Museum, to whom also we are indebt- 

 ed for the use of the drawings from which the accompanying plate has been 

 executed. A considerable number of the more interesting forms were obtain- 

 ed by Mr. Wood-Mason, who in 1872 spent two months dredging at the 

 Andaman Islands ; in the large and fine collection of shells made on this 

 occasion, particularly interesting owing to the careful manner in which the 

 specimens were preserved, their exact habitat recorded, &c., very many 

 interestino" novelties still remain to be described. We regret that figures 

 of the three new species of Marginella have been accidentally omitted from 

 the plate, we hope, however, to figure them before long with our next 

 paper. 



