360 
THE VOYAGE OF H.M.S. CHALLENGER. 
portion of a deep-sea deposit, but not like the dark-coloured clay that came up in the 
trawl, for it contained numerous casts of GlobigeHna shells, along with many angular 
fragments of basic volcanic glass. PI. II. fig. 7 shows the external aspect of four of the 
smaller nodules, while PI. II. fig. 5 shows one of the larger nodules, with portions removed 
to show the internal structure. The inner concentric layers of the great majority of these 
nodules form light brown coloured nuclei, which have frequently been compared to copro- 
lites by geologists who have examined them. These lighter layers are less than 1 mm. in 
diameter, and are arranged concentrically around altered pieces of volcanic glass, sharks’ 
teeth or their fragments. The outer layers are of a darker colour, and contain much more 
manganese than the inner ones. The appearance under the microscope of the internal 
parts of these nodules is shown in PI. XXVII. fig. 3, and in all the figures on PL XXIX. 
The t 3 'pical nodules contain about 37 per cent, of manganese peroxide, and 24 per cent, of 
ferric oxide. The structure of bone can be readily recognised in some of the nodules, 
while others appear to have been originally formed upon fragments of bone, though now 
all traces of the bone have disappeared. One of the largest tympanic bullae from this 
station {Balsenoptera) is represented in PI. VII. fig. 1. Altogether about fifty petrous 
and tympanic bones of Cetaceans were procured. Many of these were deeply imbedded 
in concentric layers of manganese, while in other cases large portions of the bone 
had been removed and substituted by depositions of manganese. 
More than fifteen hundred specimens of sharks’ teeth and fragments, over 1 cm. 
in length, were present, while immense numbers of smaller teeth and fragments were 
found in the deposit or in the nodules. Specimens of these teeth are represented in 
PI. V. figs. 6, 7, 10, and 11, and PI. VI. figs. 2, 3, 4, 5, 6, 7, 12, 18, 20, 21, and 23. 
Some of the larger teeth were surrounded with layers of manganese, but, as a rule, they 
were not so deeply imbedded as the smaller teeth and fragments. The internal portions 
of the teeth were generally filled with deposits of manganese ; the vaso-dentine and 
osteo-dentine had been entirely removed, the hard external enamel-like dentine alone 
remaining. 
The nuclei of the nodules were occasionally pieces of volcanic rock ; most of these 
had undergone considerable alteration, the glassy base having been converted into 
palagonite. Many of the specimens showed agate-like bands, similar to the specimen 
represented in PI. XIX. fig. 3 from another station. These palagonitic layers were 
soft and could be cut with a knife like cheese when taken from the sea, but they have 
since become quite Ijrittle. Two of these nuclei are represented in PI. XVI. fig. 3, 
and PI. XVII. fig. 7. Among the nodules were several bomb-like fragments about 
1 cm. in diameter, with a hard thin exterior, and a hollow interior partly filled with 
ferruginous matters. Some of the nodules contained hollow spaces, in which the 
manganese fissumed a radiate, crypto-crystalline, structure. The outside of the nodules 
was generally covered with Rliizopod tubes, or the stolons of Ily droids, and these could 
