REPORT ON THE CRINOIDEA. 303 



distichals (PI. LII. fig. 1 ; PI. LVIII. fig. 1), and I have seen a Philippine specimen with 

 two other divisions of the same character. On the other Land Actinometra rotalaria 

 and Actinometra valida have the palmar and subsequent series of three joints, the 

 axillary with a syzygy (PI. LIX. figs. 2, 3). In these two species, and also in Actino- 

 metra simplex (PI. LIX. fig. 1), the first syzygy in the free arm is that in the third 

 brachial ; but in Actinometra pulchella, Actinometra maculata, and Actinometra 

 stelligera the first two brachials above the last axillary are normally united by syzygy 

 (PI. LII. figs. 1,2; PL LV. fig. 2 ; PI. LVIII. fig. 1). This is also the case in Actino- 

 metra Solaris, Actinometra paucicirra, and Actinometra typica (PI. LIILfig. 2 ; PI. LIV. 

 fig. 1 ; PL LVII. fig. 1) ; but all these forms have a syzygial union between the two 

 outer radials, which is not the case in those belonging to Series III. 



This series thus falls into two very well defined groups according as there is a 

 syzygial union or a bifascial articulation between the first two brachials of the free arm. 

 The first of these is altogether unrepresented in Antedon, having a general formula — 



a.2.(2.2.2.)."9-. — and may be called the Stelligera- group, after a comparatively large and 



well-defined species from Fiji and Samoa (PL LVIII. fig. l). It also includes the widely 

 distributed Actinometra pulchella ; but as this is a dimorphic type which also occurs in 

 the ten-armed Echinoptera-gvoxrp, the use of its name to denote a multibrachiate group 

 might lead to confusion. 



The more normal type of bidistichate species which have the first syzygy in the third 

 brachial of the free arm is but poorly represented in Actinometra, though it includes a 

 considerable number of A ntedon- species. It is confined entirely to the Eastern Archi- 

 pelago, not occurring at all in the Caribbean Sea, where every bidistichate Actinometra 

 belongs to the protean type of Actinometra pulchella. There may be no palmars at all, 

 as in Actinometra elongata and Actinometra simplex (PL LVII. fig. 2 ; PL LIX. fig. 1), 

 or there are three with the axillary a syzygy, as in Actinometra valida, which has a 

 further division of the same character (PL LIX. fig. 3). This being the best-developed 

 species of the four members of the group which were obtained by the Challenger, it may 

 be conveniently called the Valida-gxowp, 



5. The Stelligera-grou-p. 



Two articulated distichals. The palmars and subsequent series, when present, are of 

 the same character ; but the first two brachials are united by syzygy. 



Remarks. — This is a very well defined group, although its type of structure is 

 extremely anomalous and does not occur at all in Antedon, all the bidistichate species 

 of which have the first two brachials articulated, whereas they are united by syzygy in 

 Actinometra stelligera and its allies (PL LVIII. fig. 1). 



