DEPTHS AND DEPOSITS OF THE OCEAN 173 



Carinaria cithara, Benson. 



,, punctata, d'Orbigny. 



„ gandichaiidii, Eydoux and 



Souleyet. 

 ,, atlautica, Adams and Reeve. 

 „ cornucopia, Gould. 



Atla?ita peronii, Lesueur. 



„ turriculata, d'Orbigny. 

 „ lesueurii, Eydoux and Souleyet. 

 „ involuta, Eydoux and Souleyet. 

 ,, inflata, Eydoux and Souleyet. 

 „ inclinata, Eydoux and Souleyet. 

 „ helicitioides, Eydoux and Soule- 



_ yet. 

 „ gibbosa, Eydoux and Souleyet. 



Atlanta gaudichaudii, Eydoux and Sou- 

 leyet. 



,, fusca, Eydoux and Souleyet. 



,, depressa, Eydoux and Souleyet. 



,, rosea, Eydoux and Souleyet. 



,, quoyana, Eydoux and Soule- 

 yet. 



„ mediterranea, Costa. 



,, violacea, Gould. 



,, tessellata, Gould. 



,, primitia, Gould. 



,, cunicula, Gould. 



„ souleyeti. Smith. 

 Oxy gyrus keraudrenii (Lesueur). 



„ rangii, Eydoux and Souleyet. 



The gasteropod genus lantkina is also pelagic, while the 

 species of coccolithophoridse are very numerous. 



Sea Surf a 



Fig. 142. — Diagram showing gradual disappearance of Calcium Carbonate 



WITH increasing DEPTH. 



The distribution of the dead shells of these pelagic organisms 

 in different depths is peculiar and remarkable. If we suppose 

 a cone to rise from a depth of 4000 fathoms up to within half 

 a mile of the surface far from land in the warmer regions of 

 the ocean (see Fig. 142), we shall find on the upper surface of 

 this cone, and down its sides to about 1000 fathoms, nearly 

 every shell of pelagic organisms represented in the deposit, 

 even the smallest and most delicate. At about 1500 fathoms Disappearance 

 many of the thinnest and smallest shells will have disappeared, carbl!nate\vith 

 and the Pteropod ooze passes gradually into Globigerina ooze, increase of 

 At 2000 fathoms there may not be a trace of pteropods, and *^'^^'^' 

 some of the more delicate foraminifera will also have disappeared. 

 At 2500 fathoms the larger and thicker foraminifera shells still 

 remain, and the deposit becomes a Red clay with some carbonate 

 of lime. At 4000 fathoms not a trace, or little more than a 

 trace, of these shells can be found, and chemical analysis does 

 not show I per cent of calcium carbonate. 



Now it has been shown by hundreds of observations that 



