180 TRIDACNA AND HIPrOPUS. 



that Linna3us described his T. gigas principally from shells 

 and figures of the T. squamata, probably concluding tliat 

 all Tridacnce were of one species, and tliat the larger specimens 

 had been denuded of their scales. Be that as it may, our 

 figure 1 1 represents (in characters) four shells, two in the Royal 

 Botanical Gardens, Regent's Park, and two in the Natural 

 History Museum at Kensington, the latter over three feet long, 

 while weighing only 310 pound, as against the historical 

 ' 500 pound,' and ' two feet across.' These have very deep 

 ribs, rather angular than round, and showing only on the ridges 

 strong, sharp lines, which might possibly indicate the former 

 existence of thin and close slightly projecting laminge, but 

 certainly not of large and broad vaulted scales like those of 

 the following species. 



2. SQUAJfOSA, f. 2, 7, 15, 17, Lcmiarck. — Magna subovata 

 ventricosa subsequilateralis ; costis rotundis squamatis loBvibus ; 

 concentrice leviter rugatis ; margine postico crassidentato, 

 margine antido breviter hianti ; squamis maximis fornicatis 

 extantibus arcuatis, var. (T. serrifera) squamis costarum 

 versus apicem subtrigonis, deinde obsoletis. — Although 

 generally known under the above name, the shells described 

 certainly belong to the Chama gigas of Linnaeus, with the 

 Linnsean desci-iption of which they agree. We think, how- 

 ever, it would now create more confusion to transfer the 

 name than to let it stand as it is, so as to retain the name of 

 T. gigas for the largest species. I have seen specimens 

 of T. squamosa rather more than a foot long. 



3. MUTICA, f. 1, 12, sp. La,7nk. (T. gigas, Rve., not Linn.). 

 — Ovato-oblonga, flavida, antice oblique producta, breviter 

 hians, margine hianti latissime incrassato, roseo; margine 

 ventrali; costis quatuor ad quinque latis subdepressis, dense 

 et tenuissime arcuatim squamatis. — The shells of gigantic 

 size, figured and quoted for T. gigas sp. 1, f. 11, show no 

 signs of scales, and are not oblique. Their anterior side 

 is, if anything, the shorter. The present species, on the 

 contrary, is produced on the anterior side, and has very 

 narrow scales towards the margin. It is described by 

 Lamarck as having a small hiatus ; and the specimen in the 

 British Museum, from which our figure is taken, is very 

 small in proportion to the size of the shell. Its margins are 

 thick and broad, with pinky colouring. Lamarck's specimen 



