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Show 1882.] CLASSIFICATION OF THE COMATULA. 735 the former loses its pinnule. No Crinoid with three radials ever has a pinnule on the second one; and when this becomes the hypo-zygal of a syzygy, it does not therefore lose its individuality, as is the case with the hypozygals of the brachial syzygies. Almost the same may be said respecting the first two brachials. Most Comatula have a syzygy in the third brachial with a bifascial articulation between the two preceding joints, the second only of which bears a pinnule. Hence where these two are united by syzygy, as in Act. Solaris, the first or hypozygal loses no individuality as an arm-joint. They are therefore better described as the first and second brachials, and not as a first brachial which " is a syzygy." This method has the advantage of retaining the third brachial as a syzygial joint as a condition which is common to by far the larger number of Comatula; for it is only a very few species, like Act. fimbriata and Act. multiradiata, which have a syzygy in the second brachial and a pinnule on the first. This is an entirely different type, and arises from the coalescence of the primitive second and third joints of the growing arm. I cannot, therefore, regard as satisfactory Prof. Bell's formula? for Act. Solaris, Act. brachiolata, e. g. 1.2.A'R ^ and 1.2.A'R \. For the radial axillary is not a syzygy in the same sense as the distichal axillary is in Act. parvicirra ; neither is the first brachial a syzygy in the same sense as the second or, as I should call it, the third. I am bound to say, however, that I a m in some measure responsible in the matter of the first brachials, having employed this mode of description in m y diagnoses of the Leyden Comatula '; but since then I have decided to abandon it, as will be seen from my' descriptions of Act. Solaris and Act. robusta of the Hamburg Museum, to to which I have added a few of m y reasons for the change2. The erroneous character of some of the formulas given by Prof. Bell is due, I fear, to his not having properly understood the descriptive terminology which I have been led to employ. I have endeavoured, as much as possible, to make it simply an extension of that used by Miiller; and I have consequeutly used the word " rays" in the same sense as Miiller did, as I have pointed out above3. Prof. Bell, however, seems not only to use it in a different sense himself, but also to have understood m e as doing so. The result is that many of the formulae which he has drawn up on the basis of m y descriptions are utterly at variance with them. The following is an abbreviated extract from the classification of the species of Actinometra in the Leyden Museum, together with the formulae assigned to those species by Prof. Bell:- A. Second and third radials united by syzygy. a. Ten arms Solaris. I.2.AR-. (3. Many arms. Rays may divide five times or more. First 1 Notes from the Leyden Museum, vol. iii. pp. 170-217. 2 "The Comatulas of the Hamburg Museum," Journ. Linn. Soc. Zoology, vol. xvi. pp. 514-519. 3 P. 732, note. PROC ZOOL. Soc-1882, No. XLIX. 49 |