| OCR Text |
Show 1900.] FROM THE FALKLAND ISLANDS. 563 In the discussion of the genus many of the distinctive characters of this striking species have already been described. Moreover, a very full and satisfactory account of it has been given by Dr. Pfeffer, with a great number of excellent figures. In the earlier representations both Dana and Cunningham figure the fore part of the pleon as a simple solid segment. This is the more to be wondered at on Dana's part, as he, like Milne-Edwards, figures the corresponding and similar portion of Amphoroidea typa with all the requisite detail. The specimens brought by Mr. Vallentin from the Falklands are preserved in formol and are all of a semi-pellucid orange colour, which under a lens shows a fine bordering to the segments and numerous dorsal markings of rather deeper tint, and is closely speckled about the dorso-lateral parts with minute greyish points. It is only in large specimens that it is easy to make out the sinuous suture which marks off the side-plates of the second to the seventh segments of the peraeon. The last of these segments is scarcely so wide as the second segment of the pleon. In the fourth and fifth pleopods both rami are respiratory, consisting alike of plicated lamellae, as contrasted with the corresponding appendages in some of the Sphaeromidae, in which the outer ramus or exopod is opercular. Mr. Beddard, in the 'Challenger' Isopoda, p. 147, calls attention to "a similar hypertrophy of the respiratory lamellae " occurring in the two species of Amphoroidea and in his own Cymodocea [Naesicopea] abyssorum. Two of Mr. Vallentin's specimens are of great size, the one measured being 36 m m . in length by 23 m m . in breadth, agreeing closely with the 3| centimetres of Guerin-Meneville's description. With the large specimens were two others not more than 11 or 12 m m . long, and one 23 m m . in length. Of his specimens Mr. Vallentin himself writes that the largest " was found holding on to a large drifting piece of D'Urvillea harveyi found in the harbour. The remaining specimens I secured on various occasions while collecting in m y boat. During a calm I frequently observed specimens of this species mount to the surface of the sea, as if for a supply of air, and immediately return to the bottom. The depth of water where these Crustacea were to be found was never less than two and half fathoms." ONISCOIDEA. 1822. Oniscoidea, Sars, Christiania Vidensk. Forh. no. 18, p. 58. 1893. Oniscoidea, Stebbing, Hist. Crust., Internat. Sci. Ser. vol. lxxiv. p. 420. 1898. Oniscoida, Sars, Crustacea of Norway, vol. ii. pt. 9, p. 153. 1900. Oniscoidea, H. Bichardson, The American Naturalist, vol. xxxiv. p. 301. |
