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Show 1882.] CLASSIFICATION OF THE COMATULiE. 743 The want of elasticity which renders Prof. Bell's system so misleading will not be found, I hope, in that which I am now about to explain. It has grown up gradually during seven years' work, and will meet all the variations of actual Comatula-structure with which I am acquainted, together with any others that I can imagine as possible. Some time ago I pointed out that " the first and second segments beyond every axillary, whether radial or brachial, are nearly always united together in the same manner as the second and third (axillary) radials." Further experience has shown that the " nearly " embraces several well-marked but regular exceptions to the above statement; and I have therefore drawn up the following rules, which embody the results of m y study of the group. They are not to be in any way regarded as laws of Ooma^a-structure, but merely as generalizations based upon a knowledge of some 400 species, and therefore, I hope, of some value for the purpose of classification. I. All ten-armed species of Actinometra which have the two outer radials united by syzygy, have the first two brachials united in the same way. Ex. Act. Solaris. No Antedon known. 2. All many-armed species of Actinometra which have the outer radials united by syzygy either have (a) all the ray-divisions of two joints also united by syzygy and the first two brachials similarly united ; or (/3) there may be three distichals, of which the first two are articulated and the axillary is a syzygy, while the subsequent divisions are as above. Ex. a. Act. jukesi; j3. Act. typica. 3. If the two outer radials are united by a ligamentous articu-tion, the next two joints are similarly united, whether there be ten or many arms. In the former case the third brachial is almost always a syzygy. (One of the " Blake" Comatula is an exception.) Ex. Ant. rosacea, Ant. philiberti, Act. meridionalis, Act. parvicirra. 4. In by far the greater number of Comatula which have the two outer radials articulated by ligaments and only two ray-divisions, the third brachial is the lowest syzygial joint on the arms, whether the distichal axillary be a syzygy or not ; and the two lowest brachials are articulated by ligaments. Ex. Ant. macronema, Ant. reynaudi, Act. trichoptera. Exceptions. Act. fimbriata and Act. borneensis, with some unde-scribed Antedon-species, have the second brachial a syzygy, like the distichal axillary. Act. pulchella and a new ' Challenger ' Antedon have two distichals the axillary not a syzygy, but the first two brachials united by syzygy. 5. If the two outer radials are articulated and there are more than two ray-divisions, so that palmars are present, the third brachial is the first arm-syzygy in all cases but the following :- a. T w o palmars united by syzygy ; the first two joints beyond the palmar and all subsequent axillaries are also united by syzygy. |