246 



THE VOYAGE OF H.M.S. CHALLENGER. 



A B 



Fig. 5. — The lowest pinnules of Ante- 

 don incequalis (A) and of Antedon 

 angusticalyx (B). x 3. 



or sometimes the first and second, is considerably wider than its successor (fig. 5, a). It is 

 produced towards the ventral side, so that it has a large flattened lateral surface corre- 

 sponding to those of the first and second distichals, which are both relatively and 



absolutely larger than the same parts in Antedon angusti- 

 calyx (fig. 5, b), and are also divided by a groove into two 

 portions at different levels, which is not the case in the 

 latter species. 



The number of arms which may be present in Antedon 

 in&qualis varies very considerably, just as in Antedon 

 angusticalyx. Several individuals have twenty, but fourteen 

 to sixteen is a not uncommon number, and two specimens 

 have only eleven ; so that it is quite possible that this may 

 really be a dimorphic species, and that it should find a place 

 with the ten-armed series near to Antedon basicurva, as 

 well as in the tridistichate group. Palmar series occur iu 

 two specimens. In one there are two palmars united by syzygy, just as is naturally 

 the case in Antedon distincta (PL LI. fig. l), while the other presents the type of 

 Antedon porrecta, viz., two palmars, the axillary a syzygy (PL LI. fig. 2; PL LII. fig. 3). 

 This, however, is an abnormal variation owing to the intercalation of a joint above the 

 distichal axillary ; because the first two brachials are united by syzygy in the ordinary 

 way, instead of being articulated with a syzygy in the second one as in Actinometra 

 sentosa and Actinometra midtiradiata (PL LXVI. figs. 1, 4). 



One example of Antedon insequalis and some fragments of Pentacrinns naresianus 

 were sent me with the label of Station 175; but there is no record in the Station Book of 

 their having been dredged at this Station (1350 fathoms), though there are two Comatulse 

 mentioned which reached me with the corresponding label. These are the ten-armed 

 Antedon breviradia and Antedon acutiradia (PL XL figs. 3, 5), which have the general 

 facies of abyssal forms ; and as no other Antedon with more than ten arms has been 

 obtained from a greater depth than 750 fathoms, I much doubt whether Antedon 

 inasqualis really was obtained from 1350 fathoms at Station 175. 



Both Stations 170a and 174 yielded examples of Antedon insequalis with the cysts 

 of Myzostoma tenuispinum, which also occurred on the allied species Antedon angusticalyx 

 at Station 214. One individual from Station 170a, with four cysts of this Myzostoma, 

 had another of Myzostoma willemoesii ; while at Station 174 an individual was found 

 with cysts of Myzostoma tenuispinum, and also a combined cyst of this species and 

 Myzostoma willemoesii, which type likewise occurred at Station 170a on Antedon 

 basicurva. 



