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



these two joints are articulated and the first syzygy is in the third brachial ; so that we 

 here get an approach to the characters of the Savignyi-gvowp, next to be described, 

 while the bidistichate series indicates a similar variation towards the Pcdmata-groii]). 

 In this single individual, therefore, we meet with the characters of one ten-armed and 

 three multibrachiate types of Comatuhe, and its true affinities would have been a matter 

 of some doubt, but for the presence of more normal individuals of the same type at 

 another station. 



Three Pentacrinoid larvae were also obtained off Tristan da Cunha, but at a consider- 

 ably greater depth (1000 fathoms) than the mature Antedon (Station 135e, October 18, 

 1873 ; Lit. 37° 21' 0" S., long. 12° 22' 30" W.; 1000 fathoms ; hard ground, shells, gravel). 

 The best preserved of them is represented on PL XIV. fig. 8. It appears to belong to a 

 ten-armed species, as is naturally to be expected at such a great depth ; and it has many 

 points of resemblance with the " cold area " larva which I have referred conjecturally to 

 Antedon hystrix (PL XIV. fig. 2). The basals are high and the first radials very wide, 

 while the two following joints are relatively long and narrow ; though a considerable 

 number of brachials are developed above them. These show no traces of an ambulacral 

 skeleton, however, as is the case in the youngest larva of Antedon midtispina (PL XIV. 

 fig. 5), which has only about the same number of arm-joints, though the calyx is 

 relatively much more developed than that of the abyssal larva. 



5. Antedon porrecta, n. sp. (PL LII. figs. 3-5). 

 Specific formida — A.3.2 {( p.)br} .—. 



Centro-dorsal a thick disk with the interradial angles slightly produced, and from 

 twenty to thirty long and stout cirri on its sides. They have from forty to fifty joints, 

 nearly all of which are wider than long, and produced on the dorsal side into a strong 

 pointed process. The first radials are invisible except at the angles of the calyx ; the 

 second and third both rather convex and slightly tubercular at the junction, the second 

 short, united laterally, and the axillaries broadly pentagonal, about two and a half times 

 their length. Three distichals and sometimes two palmars, each axillary with a syzygy. 

 These joints are very convex and have their inner sides flattened against one another ; 

 but this is less marked at the outside of the rays where the hypozygals of the distichal 

 axillaries and of the second palmars (or brachials) are kept apart by the large pinnules 

 on the preceding joints. 



Over twenty arms, of compressed triangular joints, which become elongated and 

 quadrate towards the end. From the third brachial onwards the middle of the distal 

 edge of each joint is raised into a strong plate, the front face of which is hollowed. 

 Beyond about the tenth or fifteenth joint this gives place to an overlap of the usual 

 character, which extends far out on the arm. 



