460 PERCY SLADEN TRUST EXPEDITION 



In Carpentaria the chitinous tubes were shown by Mobius (13) to be marked by- 

 transverse lines, and these lines probably represent ring-shaped thickenings of the chitin. 



In Polytrema they are shown to be marked by a series of rings (see Plate 32, fig. 31, 

 copied from Merkel (12)). 



In Sporadotrema (fig. 32) they are usually moniliform and frequently marked by 

 a series of ring thickenings. These facts alone, which are easily demonstrable, point 

 to the conclusion that the growth in thickness of the outer wall is not continuous but 

 marked by a series of intermittent stages of activity, and it is at each of these stages 

 of activity that the narrow calcareous shelves are or may be formed. 



VI. LITERATURE. 



1. Brady, H. B. Foraminifera. Challenger Reports, Vol. ix. 1884. 



2. Carpenter, W. B. and Jones, Rupert. Introduction to the study of the Foraminifera. Roy. 



Society, 1862. 



3. Carter, H. J. On the Polytremata. Ann. N. H. Ser. 4, xvii. 1876, p. 185. 



4. Carter, H. J. On the locality of Carpenteria balaniformis. Ann. N. H. Ser. 4, xix. 1877, p. 209. 



5. Carter, H. J. Report on Specimens dredged up from the Gulf of Manaar. Ann. N. H. Ser. 5, 



v. 1880, p. 437. 



6. Dakin, J. W. Foraminifera. Ceylon Pearl Fisheries, Vol. v. 1906, p. 240. 



7. Gray, J. E. On Carpenteria and Dujardinia. Proc. Zool. Soc. xxvi. 1858. 



8. Hickson, S. J. Report on the genus Millepora. Willey's Zoological Results. Pt n. Cambridge, 



1899. 



9. Kirkpatrick, R. A sponge with a siliceous and calcareous skeleton. Nature, May 19, 1910. 



10. Lamarck, B. P. Animaux sans Vertebres, 1816, p. 202. 



11. Lister, J. J. Foraminifera in "A treatise on Zoology" by Sir E. Ray Lankester, Part I. Fasc. 2, 



1903, p. 120. 



12. Merkel, F. Beitrage zur Kenntnia des Baues von Polytrema. Zeit. f. wiss. Zool. lxvii. 1900. 



13. Mobius, K. Beitrage zur Meeresfauna der Insel Mauritius. Berlin, 1880. 



14. Pallas, P. S. Elenchus Zoophytorum, 1776, p. 251, and in Elenchus Zoophytorum. German 



translation by Wilkens and Herbst, 1787, Part I. p. 321. 



15. Schultze, Max. On Polytrema miniaceum. Wiegmann's Archiv, 1863, p. 81. Translated by 



W. S. Dallas, Ann. N. H. Ser. 3, xii. 1863, p. 409—423, pi. 7. 



