OCR Text |
Show 1881.] THE SURVEY OF H.M.S. 'ALERT.' 11/ ESPERIA MAGELLANICA, sp. n. (Plate X. fig. 5.) Massive, subcylindrical. Surface and interior coloured by cells containing a dark pigment. Dermis fragile, with a coarse skeletal network. Main skeleton composed of a central irregular compact meshwork, which sends ramifying and anastomosing fibres to the dermis. Fibres of main and dermal skeleton stout, composed of parallel spicula with a minimum of sarcode. Skeleton-spicules of one form only, viz. spinulate, with a very slightly marked oval head ; length '4615 to \544 millim., breadth "01267 millim. Parenchyma pale yellow to ochreous brown when dry, dirty white in spirit. Flesh-spicules of two forms, viz.:-(i.) inequianchorate with the large palm about T 6y of the total length of the spicule, and its lower angles turned upwards and inwards, length '0444 to '05384 millim., scattered ; and (ii.) minute acerate, generally in bundles of two to four, sharply pointed, length '0444 to "0634, breadth about'001055 millim., scarce. Examined. In spirit, in dried state, and mounted in balsam. External Charactersl. Form irregularly cylindrical, rounded off rapidly below to a narrow base of attachment, and provided above with a slight neck at about 30 millims. from the superior extremity, where it is also rounded off. Below the neck the greatest diameter is about 60 millims., above it about 45 millims.; total length ' 120 millims. Colour in life very variable, yellow or green; inspirit grey, or dirty-white (in the dried specimens ranging from yellowish white to an ochreous brown). Surface entirely covered with mammiform papillae, from 3 to 6 millims. in greatest diameter, often coalescing into ridges; provided at the superior extremity with two circular vent-openings, respectively 7 and 8 millims. in diameter, probably much larger in life. Texture delicate, very readily compressible. Pores ? Minute Structure of Surface. Surface covered by a fragile dermis, of the thickness and texture (when wet) of blotting-paper, composed of a single layer of more or less loose spiculo-fibre, with polygonal meshes from "25 to "5 millim. in diameter, tympanized by a very pale brown sarcode more or less interspersed with loose spicules and greenish-brown granular cells, sometimes having the centre occupied by a dark patch of pigment. The minute acerates occur in bundles of two to four, occasionally scattered ; they are straight and sharply pointed at both ends. They are found at the sides of the dermal and main skeleton-fibres. They are of scarce occurrence ; and for that reason and from the need of an exceptionally good light for finding them, they constitute an inconvenient character for reference. Probably they invariably occur in the place of tricurvates in Esperia, where these are absent. Hab. Sandy Point, 7-10 fathoms; bottom, dead Balani, some of which are still, together with a good-sized Terebratula, embedded in its base. Seven dry specimens from Otter Island, Patagonia, representing ' These refer to the spirit specimen, except where otherwise stated. |