66 DR. p. n. CAllPENTEll ON SOME CKINOIDS 



larger than those obtained by the ' Porcupine,' one of the cirri 

 having 56 joints. One individual may have had but 10 arms; 

 a second had 11 and perhaps more ; but most of them are 

 broken at the base, only one distichal series of two joints being 

 left. The third had 14 arms or more, one bidistichate and three 

 tridistichate series remaining ; and of the six arms following 

 these tridistichate series, three have the first pair of brachials 



united by syzygy (A. 3. ^), while in the other three there is a 



syzygy in the second brachial (A. 3. 2 5). We thus meet with a 

 remarkable approximation to the characters of Antedon multi- 

 sjpina and A. porrecta, which, were obtained by the ' Challenger ' 

 near Tristan D'Acunha and Ascension, in depths of 550 and 420 

 fathoms respectively. The former type, like Antedon lusitanica, 

 may sometimes have no more than ten arms, as in the six 

 ' Challenger ' specimens from Ascension ; while the single indi- 

 vidual from Tristan D'Acunha possesses one bidistichate and 

 two tridistichate series, two of the arms borne on the latter 

 having a syzygial union between the first two brachials, while the 

 other two are of the ordinary type, with a syzygy in the third 

 brachial. It is, of course, possible that tridistichate series may 

 have existed in the other individuals oi Antedon lusitanica, which 

 have the arms broken at the syzygy in the third joint above the 

 costal axillary ; for there is now no means of deciding whether 

 the epizygal of this syzygy was an axillary or a simple brachial. 

 It is therefore not absolutely certain whether there are any ten- 

 armed individuals of A. lusitanica at all, as seemed to be the 

 case at first, before any tridistichate forms were known ; and it 

 is worth notice that in this one individual we meet with the 

 characters of one ten-armed and three multibraehiate types of 



Comatulse (A. 2. — A. 3. ^. — A. 3. 21), two of the latter being 



the same as occur in the single example of A. multispina from 

 Tristan D'Acunha. 



Should the tridistichate condition eventually prove to be 

 common in these two species, it may become necessary to unite 

 them under one name. At present, the main points of difference 

 between them, apart from tlje characters of the arm-divisions, 

 appear to lie in the longer cirri and less spinous arms of A. 

 lusitanica, in which also the joints of the genital pinnules, as 

 the Madeira specimens show, are somewhat produced upwards 



