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Show 558 REV. T. R. R. STEBBING ON CRUSTACEANS [May 22, the subacute apex ; the uropods have their apices subacute, that of the outer ramus the sharper and turned slightly outward. It is light coloured, with two transverse narrow dark bands. This specimen ought perhaps to be called Exosphceroma lanceolatum (White); but one has to remark that Leach describes his species as having the " last segment of pleon narrowed to a point," so that the original gigas may have been the lanceolate form. Dana speaks of the lamellae of the uropods in lanceolatum as " lanceolate, obtuse ;" and if other distinctions are not more steadfast than those based on- the apices of the telson and uropods appear to be, the two names gigas and lanceolatum may well stand in one synonymy. Colour. In formol, tbe specimens are dark or light brown, the rows of whitish markings on the peraeon being more conspicuous in dark than in light-coloured examples; the whole body is covered with minute blackish specks, the head and the peraeon-segments, however, and parts of the pleon, having clear borders which are sometimes orange in hue. Size. Length about 18 mm., breadth 11 m m. Mr. Vallentin took this species in Stanley Harbour, where it abounds. He says : " This species is usually to be found during low water under stones; but during a calm, and especially if the sun is shining brightly, they come to the surface and swim about in an aimless manner, in an inverted position, the paired appendages of the telson standing out at right angles to the body. I frequently caught them swimming in this manner when in m y boat, and when so captured they would immediately roll themselves up into a ball. On being replaced in the sea, an individual would sink a few inches, and mounting to the surface swim as vigorously as before. W h e n swimming in this manner these crustaceans would alwrays keep near the shore, where the water is not more than two fathoms in depth." Dr. Coppinger (cf. Miers, 1881) records small specimens from 9-10 fathoms at "Sandy Point." Gen. CASSIDINA Milne-Ed wards. 1840. Cassidina, Milne-Edwards, Hist. Nat. Crust, vol iii p. 223. 1843. Cassidina, Guerin-Meneville, Iconographie du Begne Animal, Crust., texte, p. 31. 1853. Cassidina, Dana, U. S. Expl. Exp. vol. xiii., Crust, p. 748. 1884. Cassidina, Studer, Isopoden Beise ' Gazelle,' p. 19. 1887. Cassidina, Pfeffer, Krebse von Siid-Georgien, p. 20. 1888. Cassidina, G. M. Thomson, Tr. N e w Zealand Inst. vol. xxi. p. 263. 1900. Cassidena, H . Richardson, The American Naturalist, vol. xxxiv. p. 222. The origin of the name of this genus is indirectly explained by Milne-Edwards when he says that in the Sphaeromicte which |