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



nine arms, not ten. The two third, brachials are replaced by a single syzygial joint, 

 which has the shape of an axillary reversed, i.e., with the angle downwards, and it bears 

 a pinnule on the left side. The following arm-joints are of the usual character. A 

 somewhat similar monstrosity was noticed in Part I. (p. 347) as occurring in Metacrinus 

 angulatus, and Levinsen 1 has figured one of much the same in kind in Antedon 

 eschrichti. 



Two larvae which were dredged by the "Porcupine" in the "cold area" come to be 

 referred to Antedon hystrix by a sort of process of exclusion, as I cannot identify them 

 with the Pentacrinoids either of Antedon tenella or of Antedon eschrichti, with which 

 latter species Antedon quadrata is very closely allied. 



No. 1 (PL XIV. fig. 2). In this larva there is no trace of cirri, the anal plate 

 separates two of the radials, and the arms are just beginning to sprout from the radial 

 axillaries. There are five discoidal joints at the top of the broken stem, which is much 

 more robust than that of the corresponding stage of Antedon rosacea, while the head, 

 which exceeds 1 mm. in length, is nearly twice as big as that of the rosacea-larva. The 

 orals, which rest directly on the radials, recall those of Hyocrinus, having a deep median 

 groove, only more marked than in that type, with the lateral edges folded over somewhat 

 strongly. This character is less marked in the rosacea-larva, and the orals of Antedon 

 tenella in the first and second stages of the Pentacrinoid were described by Sars 2 as 

 convex. In its general appearance the Pentacrinoid now under consideration comes 

 between the second and third stages of the larvae described by Sars, but is of larger size 

 than both. Sars gives the measurements of the head as 0"5 and 0'75 mm. respectively, the 

 larger individual having six brachials above the axillaries ; but in the " Porcupine " larva 

 there are only two short brachials, and the head reaches 11 mm. It resembles the larva 

 of Antedon tenella in the great height of the basals, but differs from it altogether in the 

 unusual shortness and width of the radials, especially the first. These plates are 

 relatively wider than the corresponding plates in an older stage of Antedon tenella, 

 whereas they would be relatively longer did the larva belong to this species. A similar 

 difference between the radials of two other larvae in almost the same stage of development 

 will appear on comparison of figs. 8 and 9 on PI. XIV. I think it not improbable that 

 this "Porcupine" larva may be a younger stage of that represented in PI. XIV. fig. 3, 

 which was also dredged in the cold area during the cruise of 1869. 



No. 2 (PI. XIV. fig. 3). The stem, which is broken some 20 mm. from the calyx, 

 forms an attachment to a hydroid-tube at about its thirtieth joint, and is continued 

 downwards half-a-dozen joints further. There are six discoidal joints below the rudi- 

 mentary centro-dorsal, which bears the sockets of five short cirri. Only one of them 

 remains, however, reaching up to the top of the basals, which make up about half the 



1 Op. cit., p. 35, Tab. xxxv. fig. V. • 



2 Memoires pour servir a la connaissance des Crinoides vivants, Ckristiania, 1868, p. 48. 



