20 THE VOYAGE OF H.M.S. CHALLENGER. 



"Valorous" dredgings in Baffin's Bay (lat. 62° 6' K, depth 1350 fathoms, bottom 

 temperature 34°"6 Fahr.), as well as at two Stations in the North Atlantic, both in the 

 parallel of 56°, — No. 12, depth 1450 fathoms, and No. 13, depth 690 fathoms.^ It has been 

 only once brought up in the Challenger expedition, viz., at Station 44, off Cape 

 Hatteras, on a bottom of 1700 fathoms, over which creeps (there is strong reason to believe) 

 an under-flow of cold water from the Arctic basin. It has since, I understand, been 

 found plentifully in a dredging taken by the " Travailleur," in the Bay of Biscay (Fosse 

 de Cape Breton), at a depth of 1200 fathoms. — It would seem, therefore, that Orhitolites 

 tenuissima has its proper home on the sea-bottom of the deeper parts of the North Atlantic, 

 where the temperature ranges from 37° Fahr. downwards ; but that it is also capable of 

 living, not only in much shallower, but also in much warmer waters. For the temperature 

 of the Mediterranean and ^gean, even at depths below 100 fathoms, is never less than 

 54° ; whilst on the shallow bottom of Setubal Bay, and the shore-slope near Carthagena, 

 the summer temperature must be considembly higher. 



Looking to the singular retention, in this beautiful Orbitoline, of the MUioline type, 

 its derivation from which may now be confidently afiirmed, and also to that elongated 

 form of its chamberlets which seems to mark it out as more nearly related than either of the 

 other " simple " types to PeneropUs, the probability seems strong that it was a very early 

 form; and although no specimens of it have yet been met with in the fossil state, its 

 absence from the Geological Record may be considered as sufiiciently accounted for by 

 its extreme fragility. I need scarcely point out how completely the idea of its antiquity 

 is borne out by its j)ersistence in the abyssal depths of the North Atlantic,; — the home of 

 so many other early types of animal life. 



2. Orhitolites vim-gmalis, Lamarek (PL III. figs. 1-7, PI. IV. figs. 1-5).. 



Orhitolites marginaUs, Lamarck, Syst. des Anim. sans Vertebres [1801], 



Sorites orbiculiis, Ehrenberg, Familien uud Gattungen der Polythalamien. Abhandl. der konig. 



Akad. der Wissenschaften zu Berlin, L839. 

 OrlicuUna complanata, 'Williamson, Txans. Micr. Soc, vol. iii., 18512, p. 115. 



This species was established by Lamarck on the basis of specimens discovered by 

 M. Sionest of Lyon, attached to corallines, fuci, &c., in the Mediterranean ; and was the 

 only recent type of the genus then known. Lamarck's description of it — utrinque pla7ia, 

 margine poroso — is quite insufiicient to differentiate it either from the preceding or from 

 the species I shall have subsequently to describe ; but as no other Orbitolite is known to 

 inhabit the Mediterranean or ^gean, there is no difiiculty in specifically identifying the 

 Lamarckian type with the more highly developed examples of it which are found in the 

 Red Sea, on the coast of Australia, in the Philippine Sea, and on the Fiji reef. The 



* Proc. Roy. Soc, June 15, 1876. 



