210 Mr. H. J. Carter on the 



I now find, however, that the type specimens of Polytrema 

 halaniforme in the British Museum partly cover both valves 

 of Mytilicardia variegata in company with Polytrema minia- 

 ceum, labelled " Carpenteria, Philippines." 



There is also another specimen on one valve only of a M. 

 variegata ; and this, too, is in company with specimens of 

 Polytrema miniaceum. It is labelled '"'' Dujardinia^ Mediter- 

 ranean." 



Going to " Case 38 " in the Shell-Eoom, we there find one 

 specimen of Mytilicardia variegata with nothing upon it (it 

 may have been cleaned) — and next to it a specimen from "Port 

 Essington" (north coast of Australia), apparently bearing only 

 the remains of P. halaniforme. 



Close by may also be seen a specimen of Mytilicardia caly- 

 eulata, labelled " Port Natal and Mediterranean ; " and in the 

 drawer below, a specimen of Mytilicardia variegata covered 

 with Polytrema miniaceum, but no P. halaniforme, — labelled 

 "KedSea." 



Following Chenu's representations, I have stated that my 

 specimens of Polytrema halaniforme are on Mytilicardia caly- 

 culata ; but I can see no difference between Chenu's figure of 

 M. calycidata (' Manuel de Conchyliologie,' 1862, t. ii. p. 135, 

 fig. 650) and my own specimen of tliis bivalve, which, again, 

 is identical with that in the British Museum labelled Mytili- 

 cardia variegata ; yet the difference between this and M. caly- 

 cidata in the British Museum is very evident, although not 

 very great. 



In the drawer of the Case mentioned is another specimen 

 of M. variegata covered with Polytrema miniaceum, labelled 

 " Port Essington ; " and a crab-claw submitted for my exami- 

 nation by Dr. Carpenter is also in the same state, but bearing 

 among the specimens of P. miniaceum also one of P. halani- 

 forme. 



My inference, then, altogether is, that we should seek for spe- 

 cimens of Polytrema halaniforme on Mytilicardia variegata 

 &c. from the Polynesian Seas. 



It may be questioned whether P. halaniforme exists in the 

 Mediterranean Sea, although P. miniaceum is abundant there 

 and apparently in every sea within the parallels of 35° north 

 and south of the equator. 



From what has been above stated, the presence of P. mini- 

 aceum, on account of its red colour, might prove serviceable in 

 finding out specimens of P. halaniforme, which, being colourless 

 and very like a Balanus, are equally likely to escape notice, 

 since the habitat of the latter is not confined to Mytilicardia 

 variegata in the Polynesian Seas, but, according to the late Dr. 



