118 THE VOYAGE OF H.M.S. CHALLENGER. 



lusitanica, either that the twelve-armed condition is a monstrosity, or that Antedon 

 multispina is a dimorphic species. In the latter case it is rather a curious one. For in 

 all the four arms which are borne on the two distichal axillaries (PI. LXIX. figs. 1, 2) 

 the first pair of brachials are united by syzygy just as in Antedon angusticalyx, 

 Antedon distincta, and Antedon ineequalis (PI. L. fig. 1; PL LI. figs. 1, 2), which do 

 not conform- to the ordinary rule of a syzygy in the third brachial. 



Antedon multispina differs from the species already described in the preceding pages 

 in the small number of its cirrus-joints, which does not seem to exceed thirty. It 

 resembles most of them, however, in having a relatively small pinnule on the third 

 brachial, which is more like its successors (PI. XIII. fig. 3) than its predecessor. The 

 two outer radials, especially the second which are very short, can hardly be described as 

 wall-sided ; but this feature is very marked on the outer side of the first brachials and 

 on the inner side of the second and the hypozygals of the third brachials (PI. LXX. 

 figs. 1-3), while the first pinnules of adjacent rays are flattened laterally against one 

 another and their inner sides are slightly cut away at the base, so as to recall the condition 

 of Antedon incerta and allied species (PI. XVIII. fig. 5). 



From about the twelfth brachial onwards the third and next following pinnule-joints 

 are expanded for the protection of the genital glands, having a broadly V-shaped section, 

 though this is less marked than in Antedon gracilis (PL XV. fig. 4). 



Besides the three young individuals of Antedon multispina, one of which is figured 

 on PL XIII. fig. l,the Challenger also dredged three Pentacrinoid larvae, which presumably 

 belong to this species, as it is the only ten-armed form met with at this station. They 

 are relatively much larger and more robust than the corresponding larval stages of 

 any other species which I have seen, with the exception of Antedon eschrichti. 

 Figs. 3-7 on PL XIV. represent five larvae, all equally magnified, which belong respect- 

 ively to Antedon hystrix ? (fig. 3), Antedon tenella (fig. 4), and Antedon multispina 

 (figs. 5-7). Figs. 3-5 illustrate almost the same developmental stage in the three 

 different species, that namely when the first cirri make their appearance and a fair 

 number of arm-joints have been formed. Of the three larvae, that of Antedon tenella 

 is the oldest, having pinnules on the outer parts of the young arms, but it is altogether 

 less robust than that belonging either to Antedon hystrix? or to Antedon multispina. 

 The latter is remarkable for the shortness of its stem, which has only thirteen joints 

 below the centro-dorsal, the two lowest being quite short and resting on a large and 

 expanded dorsocentral plate (PL XIV. fig. 5). The centro-dorsal is a thin plate, but 

 little larger than the joints below it, and the rudiments of three cirri have appeared upon 

 it, the positions of the other two being indicated by imperfect sockets. In the next 

 stage (PL XIV. fig. 6) the first pinnules have appeared on the arms, not at their bases, 

 but about the eleventh or twelfth brachial, and the five radial cirri which were* first 

 formed are well developed so far as can be judged from their basal joints, which is all 



