1882.] CLASSIFICATION OF THE COMATUL^. 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 Comatulce 

 have a syzygy in the third brachial with a bifascial articulation be- 

 tween 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 syzy- 

 gial joint as a condition which is common to by far the larger num- 

 ber of Gomatidee ; 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 formulse 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 am in some measure respon- 

 sible in the matter of the first brachials, having employed this mode 

 of description in my diagnoses of the Leyden ComatulcB ' ; but since 

 then I have decided to abandon it, as will be seen from my descrip- 

 tions of Act. Solaris and Act. robiista of the Hamburg Museum, to 

 to which I have added a few of my reasons for the change ". 



The erroneous character of some of the formulae given by Prof. 

 Bell is due, I fear, to his not having properly understood the de- 

 scriptive 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 consequently used the word " rays " 

 in the same sense as Miiller did, as I have pointed out above ^ 

 Prof. Bell, however, seems not only to use it in a different sense him- 

 self, but also to have understood me as doing so. The result is that 

 many of the formulse which be has drawn up on the basis of my 

 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 

 formulse assigned to those species by Prof. Bell : — 



A. Second and third radials united by syzygy. 



a. Ten arms Solaris. 1.2.A'R~. 



13. Many arms. Rays may divide five times or more. First 



'■ Notea from the Leyden Museum, vol. iii. pp. 170-217. 

 ^ "The Comatulis of the Hamburg Museum," Joum. Linn. Soc. Zoology, vol, 

 xvi. pp. 514-519. 

 ^ P. 732, note. 



Prog. Zool. Soc— 1882, No. XLIX. 49 



