38o Mr. Cosmo Melvill on the 



beautifully executed plates than its letterpress, and the 

 representation of L, prismaticus leaves nothing to be 

 desired, as it was taken from a very fine specimen. At the 

 sale of Mr. G. F. Angas' collection, in 1870, I acquired a 

 beautiful example, with operculum, which shows the dark 

 cobalt to indigo reflections to perfection — and have three 

 others, which shew it in greater or less degree. The 

 epidermis removed, all chance of obtaining these radiant 

 results vanishes. Mr. W. Harper Pease {Proc. Zool. Soc, 

 1865, pp. 53 — 54) gives full details of the exact localities for 

 the above (see Catalogue), and compares with it L. gemmatiis 

 (Reeve) \L. peristernia\ violaceus (Reeve) ^ndgibbus (Pease), 

 the latter being then described for the first time. In his 

 opinion the four are nearly allied, though differing some- 

 what in form, from the fact that this prismatic iridescence 

 is present in the epidermis of each. As we have said, the 

 reflections in the type species are of a deep azure blue, 

 L. vw/aceus possesses gold and silvery shades of purple and 

 green, geminatus^ and gibbits a fainter and not very con- 

 spicuous radiance. This only, in every case, when the 

 epidermis is wetted or oiled. 



I have often noticed, in deep tidal pools round our coasts, 

 and likewise in those of other countries, certain marine 

 Algae, appearing beautifully prismatic in the water, steel 

 blue or sea-green being the predominant reflections, the effect 

 of which vanishes, however, entirely and immediately they 

 are withdrawn from their native element into the open air. 

 Such are the British Rhodyrnenia palmata (Grev.) and, 

 above all, Nitophyllum laceratiim, (Grev.) Chondrus crispus 

 (Lyngbye), and Cystoseira ericoides (Agardh). It is possible 

 that the Latirus prismaticus^ and the other species with 

 iridescent epidermis, feed exclusively on Algae possessing 

 this peculiarity, and so a colour resemblance has been given 



* While these pages were in the press, Mr. J. R. Hardy, of Owens 

 College Museum, has shewn me a beautiful specimen of L. genimatus, showing 

 prismatic reflections almost equal to L. prismaticus, from the collection of 

 Mr. Lionel Adams, of Penistone, nephew of Messrs. H. and A. Adams. 



