GLOBIGERINIDA ; GLOBIGERINA; CARPENTARIA. 501 



chamber -with, porous walls, and a simple circular aperture that is > 

 frequently replaced by a number of large pores scattered through- f 

 out the wall of the sphere. There is some reason to think that 

 Orbulina is really nothing else than the detached Reproductive 

 segment of Globigerina ; which consists of an assemblage of such ( 

 chambers (Fig. 12), coherent externally into a more or less regular 

 Turbinoid spire, but all of them opening separately into a common 

 ' vestibule ' which occupies the centre of the under side of the 

 spire. This Genus has recently attracted great attention, from 

 the extraordinary abundance in which it seems to occur at 

 great depths over large areas of the Ocean-bottom. Thus its 

 minute Shells have been found to constitute no less than 97 per 

 cent, of the ' ooze ' brought up in the scoop attached to the deep- 

 sea Sounding apparatus, t from depths of from 1,260 to 2,000 

 fathoms in the middle and northern parts of the Atlantic Ocean, 

 where the presence of this type in such quantities seems to follow 

 the course of the Gulf-stream. The surface-layer of this ooze 

 consists of living Globigerina? ; whilst its deeper layers are almost 

 entirely composed of dead shells of the same type. And it is 

 probable that these Globigerina? form an important article of sus- 

 tenance to the forms of Star-fish which have been brought up alive 

 from the same ocean-depths. 



384. A very remarkable type has recently been discovered ad- 

 herent to Shells and Corals brought from tropical seas, to which 

 the name Carpentaria has been given ; this may be regarded 

 as a highly developed form of Globigerina, its first-formed portion 

 having all the essential characters of that genus. It grows at- 

 tached by the apex of its spire to Shells, Corals, &c. ; and its 

 later chambers increase rapidly in size, and are piled on the earlier 

 in such a manner as to form a depressed cone with an irregular 

 spreading base. The essential character of Globigerina — the sepa- 

 rate orifice of each of its chambers — is here retained with a curious 

 modification ; for the central Vestibule, into which they all open, 

 forms a sort of Vent whose orifice is at the apex of the cone, and is 

 sometimes prolonged into a tube that proceeds from it ; and the 

 external wall of this cone is so marked out by septal bands, that it 

 comes to bear a strong resemblance to a minute Balanus (acorn- 

 shell) for which this type was at first mistaken. The principal 

 Chambers are partly divided into Chamberlets by incomplete parti- 

 tions ; and the whole assemblage of cavities is occupied in the 

 living state by a Spongeous substance beset with Siliceous spicules.* 



385. A less aberrant modification of the Globigerine type, how- 

 ever, is presented in the two great series which may be designated 



* A detailed account of this very curious Organism, which seems to 

 constitute a connecting link between Sponges and Foraminif era, will be 

 found in the Author's Memoir in the " Philosophical Transactions " for 

 1860, and in his "Introduction to the Study of the Foraminif era," pub- 

 lished by the Ray Society. 



