174 



THE VOYAGE OF H.M.S. CHALLENGE!*. 



contents of a tow-net attached at the weights in front of the trawl, and was mounted on 



a glass slide as a microscopic preparation. As the specimen shows a structural feature 



unknown till that time among Echinodermata, the follow- 

 ing details from Mr. Lyman's paper 1 will be interesting : — 

 " Long after the main collection of the Challenger 

 Expedition had arrived, there were sent me several 

 glass slides containing additional specimens of Ophiu- 

 rida?. One of these, hastily examined with a weak 

 lens, I labelled Ophiomyces, and set aside for further 

 study. In the very last cast made by Mr. Alexander 

 Agassiz, during the " Blake " Expedition of 1878-79, near 

 the Barbados, and in 82 fathoms, there came up a small 

 soft Ophiuran, which seemed, under the microscope, to 

 have little tufts resembling bunches of simple hydroids on 

 the sides of the arms. More careful search, with a higher 

 power, showed that these were bunches of minute spines, 

 each enclosed in a thick skin-bag, and that they had a 

 most extraordinary form, resembling long-stemmed agarics, 

 or parasols with small shades. On going back to the 

 Challenger Ophiomyces, this too exhibited the same spines, 

 and a third species, also brought back by the Challenger, 

 was found with similar appendages. Their form, however, 

 was not the most curious thing. It was by their arrange- 

 ment in two, or even three, parallel vertical rows, that 

 they wholly differed from all Ophiuridse hitherto known. 

 For, with all the variety exhibited by the hundreds of 

 living species, there is not one that departs from the 

 unvarying single row of articulated spines. Not even the 

 double rows of hook-bearing grains among the Astro- 

 phytidse would be homologous, because these grains are 

 not attached to the side arm-plates. In one species, these 

 parasol-spines stood side by side with the normal arm- 

 spines (Ophiotholia), while in the two others (Ophiohehis), 

 they took the place of the normal spines. Among known 

 Echinodermata I have been able to find only a single 



instance of a somewhat similar spine, or pedicellaria. This is in Aceste bellidifera, Wyv. 



Thorns. 2 The question whether these novel shapes are spines or pedicellarise is not a 



1 A Structural Feature, hitherto unknown among Echinodermata, found in Deep-sea Ophiurans, Boston Soc. Nat, 

 Hut. (Anniversary Memoirs), 1880. 



2 Agassiz, ZooL Chall. Exp., part ix., pi. xl. fig. 60, 1881, 



Fig. 73. — Ophiotholia sn/iplicnns, Lym. 

 The entire animal, ten times the natural 

 size, seen in profile, with its arms and disk 

 stretched upward, and its mouth angles 

 turned downward and outward, and armed 

 with their mouth papillre like those of 

 Ophimnyces. On the outer arm joints 

 are the small parasol spines. Station 296, 

 November 9, 1875, southwest of Juan 

 Fernandez, lat. 38° 6' S., long. 88° 2' W. ; 

 1825 fathoms. 



