PEILE : SOME NOTES ON RADUL.E. 15 



(a) There are twin rhachidians, rather smaller than the normal 

 but having their main cusps longer and more pointed. 



(b) On one side there is a normal lateral but only one marginal 

 instead of two. 



(c) The other side has- two rather small laterals and the inner 

 marginal is rather small. 



Other records to hand include Gwatkin specimens of Maizania 

 waMhergi (Benson) and Theodoxis jordani (Sowerby), with no trace 

 of a rhachidian, and, in my own collection, Gena strigosa, A. Adams, 

 with four laterals on one side and the normal number five on the 

 other. 



IV. AcMiEA FLUViATiLis, Blanford. 

 The Gwatkin collection contains a specimen of the radula of this 

 species without locality, the type locality being the Irrawady River. 

 Though it agrees with Acmcea in the number and arrangement of the 

 teeth, their form is so remarkable as to warrant the creation of a new 

 gen as which I propose to designate : — 



POTAMACM^A. 



Type species fluviatilis, Blanford. Only the plan view of the 

 teeth can be determined from the specimen examined and figured 

 (Fig. 3). They difier from those of any other known in being 

 broad and straight with saw edges. The habitat of the animal is 

 peculiar in that, as far as is known, it does not live in salt water. 

 Dr. Annandale informs me that a species lives under similar con- 

 ditions in the Hoogly, and that his collectors have found it on 

 human corpses. It will be interesting to discover whether this 

 species is the same as that of the Irrawady and whether the latter 

 is prone to a carnivorous diet. 



V. Some Australian Eadul^. 



The material from which the preparations were derived was 

 kindly put at my disposal by Mr. T. Iredale, who received it from 

 Mr. Roy Bell, who obtained it at Twofold Bay, N.S.W. The slides 

 of the radulse figured are now in the Natural History Museum. 



1. The shell described by Pilsbry as Acmcea saccharina, L., var. 

 perplexa, Pilsbry, = ? Patella octoradiata, Hutton (vide Manual of 

 Conchology, vol. xiii, p. 51), proves to be a Patella with a radula 

 having a small bat well-marked rhachidian (Fig. 4). The radula 

 somewhat resembles a specimen in the Gwatkin collection labelled 

 P. pentagona, Reeve, Manila, and specimens labelled P. cretacea, 

 Reeve, Tonga. There is also some resemblance to Patellidea 

 granulans (L.), as figured by Troschel in Thiele, vol. ii.^ 



^ This figure is not copied in Manual of Conchology, vol. xiii, pi. lii, fig. 6, 

 as stated in the index, and in the text p. 172. Fig. 6 is a copy of Troschel's 

 Ancistromesus chitonoides (Reeve). 



