LUCINA. 83 



what closed anteriorly and posteriorly, leaving a large pedal 

 opening in the centre of the ventral range ; no siphonal pro- 

 cess appears, not even an orifice ; the branchiae must be sup- 

 plied through the pedal aperture. The body is very small, 

 pale brown, with the intestine passing through the liver. There 

 are two subquadrangular branchiae, and two palpi, on each 

 side ; the former are finely pectinated above, and smooth on 

 the under surface ; the palpi are moderately long and pointed, 

 as well as striated on one side ; both are of a good brown 

 colour. The foot is clear white, moderately long, flattish, and 

 lanceolate-shaped laterally and at the point. 



The L. rotundata has been consigned to a new genus, termed 

 Diplodonta, by the learned authors of the ' British Mollusca/ 

 on our authority as to the animal structure. I feel pleasure 

 that they state this allocation is provisional, as the animal 

 presents anomalies of so peculiar a nature, that malacologists 

 are earnestly called on for a minute examination of this curious 

 creature. I accept the invitation, and hope either to confirm 

 my observations, or offer rectifications. This species has many 

 of the characters of the type, L. borealis, and I think, whether 

 my notes are confirmed or not, it must be considered an out- 

 lying branch of this family. The hinge and other distinctions 

 will not, in any case, allow of the suggestion of handing over 

 this species to the Kelliada. 



Fresh, though dead shells are commonly taken in the coral- 

 line zone at Exmouth, but I never met with more than two 

 specimens alive ; the one examined was less than half an inch 

 diameter. 



The following addenda were made at Exmouth on the 22nd 

 July, 1850, a year after the preceding notes. The account in 

 the ' British Mollusca/ vol. ii. p. 65, of the Diplodonta rotun- 

 data, our Lucina rotundata, was made from the sketch above. 

 The possession of a live specimen of f of an inch diameter, 

 enables me to say that my account, as far as it goes, is nearly 

 correct ; but I can offer some amplifications, particularly on 

 that important organ the foot. Beyond all doubt, I state, 

 that there are, on each side, a pair of branchiae and palpi; 

 the branchiae are transverse, though somewhat elongated, 



G2 



