42 BULLETIN OF THE 



Residue, 52.36 per cent, a green sand, consists of Minerals [40.00], m. di. 

 0.3 mm., many glauconitic grains, quartz, mica, felspars, hornblende, magne- 

 tite, augite, phosphatic grains. Siliceous organisms [8.00J, Sponge spicules. Dia- 

 toms, Kadiolarians, and many fine glauconitic casts of Poraminifera. Fine 

 Koshings [4 36], traces of argillaceous matter, fine mineral particles, fragments 

 of Diatoms, and much green amorphous matter. 



Station 317. — Lat. 31° 57' N. Long. 78° 18' 35" W. Depth, 333 

 fathoms. From this place, where the ground was said to be hard, there 

 was procured a very remarkable concretion that appears to have been 

 formed in the position from which it was dredged. 



This was irregular in form, the greatest diameter being about nine 

 inches, and of a mottled black, red, and brown color. The surface was 

 somewhat irregular, and presented many ovoid, smooth projections, the 

 largest of which were about one centimetre in diameter. The whole 

 mass was overgrown with sponges, corals, and annelids. Imbedded in 

 the concretion were two sharks' teeth, resembling Lamna, the largest 

 being 2\ inches in length and one inch across the base. This tooth is 

 similar to many found by the '•Challenger" in great numbers in the 

 greater depths of the Central Pacific, frequently forming the centres of 

 manganese nodules. In the specimens from the deep water of the 

 Pacific the interior of the tooth had been in every instance completely 

 removed, only the hard outer dentine remaining. In the tooth imbedded 

 in this concretion, on the contrary, the vaso-dentine of the interior of 

 the tooth is well preserved, in this respect resembling the sharks' teeth 

 of the same kind found in various tertiary deposits, as for instance in 

 South Carolina and in the Island of Malta. The vessels of the tooth are 

 infiltrated with peroxide of iron and manganese and phosphate of lime. 



The whole mass has a breccia-like appearance, the several fragments 

 being cemented by deposits of carbonate of lime and manganese per- 

 oxide. When thin sections are pi'epared and examined with the micro- 

 scope, the preparation has a variegated appearance ; all the grains being 

 closely cemented together. There are numerous sections of pelagic and 

 other calcareous Foraminifera, of Pteropods, and fragments of Echino- 

 derras. The interior of the Foraminifera is sometimes completely filled 

 with calcite, and the same crystals are found cementing many of the 

 fragments of which the rock is composed. Small fragments of quartz, of 

 felspars, and of zolene are also seen in the sections. But the most char- 

 acteristic element is formed by small rounded gi'ains of a brownish or 

 yellow-green color, having much the aspect of glauconite, which is also 

 present. Chemical reactions show that these grains are phosphatic. 



