Again, I possess a group of remarkably fine specimens given me by Mr. L. Reeve, from the southern ocean, (as I infer from a young _Lepas australis_ adhering to them,) in which all the individuals, young and old, are characterised as follows:--Scuta, with the lateral lobe generally broad, but to a very varying extent, with the upper and lower lobes extremely sharp. Terga separated from the scuta, by one and a fourth of their own length, and by their own length from the carina; somewhat acuminated at both ends, nearly straight, with a very slight shoulder near the umbo. Carina equalling the terga in length, and about three fourths of the length of the scuta; neither the upper nor lower point much acuminated. All the valves most imperfectly calcified: in one specimen, the scutum on one side was simply horny, without a particle of calcareous matter. The summit of the capitulum nearly intermediate in outline between the common square, and bluntly-pointed form of _var. chelonophilus_. I compared the cirri and trophi with those of a common variety, and could detect not the smallest difference. This variety differs from _var. Olfersii_, in the less development of its carina, and from _chelonophilus_, in the greater development of its carina, and especially of its terga. It would appear as if the great variability of the valves was connected with the absence of calcareous matter. 3. CONCHODERMA HUNTERI. Pl. III, fig. 3. CINERAS HUNTERI. _R. Owen._ Cat. Mus. Coll. of Surgeons, (1830), Invert. Part I., p. 71. _C. valvis angustis: scutis trilobatis, prominentiâ laterali non latiore quam inferior: tergorum parte superiore pæne rectangulè secundùm aperturæ marginem flexâ: carinâ valde arcuatâ: pedunculo brevi, in capitulum coalescente._ Valves, narrow: scuta, trilobed, with the lateral lobe not wider than the lower one: terga, with the upper part bent almost rectangularly along the margin of the orifice: carina considerably arched: peduncle short, blending into the capitulum. No filament attached to the pedicel of the second cirrus. _Var._--Carina absent; scuta, with the upper lobe absent; terga, with the rectangular projection little developed. Attached to the skin of a snake, probably the Hydeus or Pelamis bicolor, and therefore from the tropical Indian or Pacific Oceans. Mus. Coll. of Surgeons.[40] [40] I owe to the kindness of Professor Owen, an examination of these specimens, and information regarding them. _Capitulum_, with the membrane very thin; summit obtusely pointed. Valves linear and thin. _Scuta_, elongated, flat, with the upper projecting lobe rather more acuminated than the lower, and equalling it in length; lateral lobe not wider than the lower, and about as long as it, forming an angle of about 55° with the upper one.