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Show 1879.] MR. F. J. BELL ON THE ECHINOIDEA. 249 of I. mitrata, a very marked difference presents itself, which that the Kina-Balu bird belongs to a new species. Although similar to I. mitrata in its general coloration and white-edged quills, it is distinguished at once by its chestnut ear-coverts, while the chin and fore part of the cheeks are also chestnut. 16. TURDUS FALLENS. Turdus pollens, Pall.; Salvad. torn. cit. p. 256. An adult specimen sent by Mr. Treacher. 17. MoNTICOLA SOLITARIUS. Monticola solitaria (P. L. S. Mull.), "Walden, Tr. Z. S. ix. p. 192. A specimen sent by Mr. Treacher. This is the second occurrence of the bird in Borneo, the first having been recorded by me under the name of Monticola pandoo (Ibis, 1877, p. 13), from Mr. Alfred Everett's Bintulu collection. Mr. Treacher's specimen is in full blue-and-red plumage, with the usual margins to the feathers found in the winter dress. 3. Observations on the Characters of the Echinoidea.-I. On the Species of the Genus Brissus, and on the allied forms Meoma and Metalia. By F. J E F F R E Y B E L L , B.A. Magdalen College, Oxford, Zoological Department, British Museum. [Eeceived February 18, 1879.] In an examination of the specimens of Echinoidea in the British Museum I have had as my chief aids the ' Catalogue of the Recent Echinoidea in the Collection of the British Museum,' part i., by Dr. J. E. Gray (London 1855), and the ' Revision of the Echini' of Prof. Alexander Agassiz, published at the University Press, Cambridge, U. S., 1872-73. It has been a difficult matter at times to hold a balance between systematists of such widely different principles. Agassiz recognizes three species of the genus Brissus-B. obesus, Verrill, B. carinatus, and B. unicolor. As the Museum collection not contain any specimen of B. obesus, I shall confine what I have to say to the two latter, which are thus distinguished by Agassiz (p. 357):-"The only features by which I am able to separate the two undoubted species of Brissus (B. carinatus and B. unicolor) are the proportions of the anterior and posterior pair of ambulacra, and the striking difference in the course of the fasciole in the anterior part of the test. In B. carinatus the posterior ambulacra are much shorter than the anterior pair, while they are nearly equal in B. unicolor. There is but one reentering angle in anterior part of fasciole on the anterior interambulacra, while there are two in B. carinatus." Though Dr. Gray distinguishes a larger number of species (just the same, indeed as Agassiz and Desor), he seems to have had a better |