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Show 1879.] MR. F. J. BELL ON ECHINOCIDARIS. 437 ningham's collection, one of which bears evident marks of having undergone examination. It is obvious that the question could not be left in this state. It seemed now necessary to see how far the number of anal plates varied in various species, and whether the character in question had not been definitely attained to by this species only, or whether in other species also there was at times a return to the possession of the large number of plates which are so commonly found in nearly all Echi-nida. With this object in view, I have examined all the specimens of the genus Echinocidaris in the Museum ; and the accompanying Table will, I think, show that the work was worth the doing. In addition to the nine specimens here noted, there is a specimen of E. pustu-losa ("grandinosa") in which only three plates are present: one of these is very small; and it is also evident that two bave dropped away. I have been enabled to examine some fifty-four specimens in which the anal plates are preserved; and the "number of specimens " in the following list gives the number of specimens in the set from a given locality or collection. Name of species. Locality. E. dufresnii Port Otway. ,, Shell Bay. ,, Sandy Point. ,, Otter Islands. E.stellata ? E. nigra Coquimbo. „ (or sp. closely allied) ? v J J 9 yy • • In the three specimens of E. dufresnii and the one specimen of E. pustulosa (juv.) received from the * Challenger' Expedition, the number of anal plates is normal. With regard to this Table we have to note (1) the reduction of the plates below the normal number, as obtaining in three specimens not all of the same species ; (2) that the specimen of E. pustulosa (yrandinosa) already referred to, and that of E. nigra from Coquimbo prevent our limiting the possession of five plates to E, dufresnii; while the specimens with six and with ten plates are most remarkable, inasmuch as in both cases there are two plates which retain the proper Echinocidarid character. No normal specimen seems yet to have been observed so young as not to have attained its four anal plates. In conclusion I think it well to abstain for the present from any speculation on the matter, and shall be satisfied if I direct the attention of echinologists to the point in question. No. of specimens. 5 3 1 1 1 1 10 1 8 Varieties. One with five anal One with five One with three One with three One with five One with five One with six One with ten One with three plates JJ D f) j • JJ 1J |