294 



THE GEOLOGIST, 



lata is very abundant in the Gault, Upper Greensaud, Chalk-marl, and Chalk. Its oc- 

 currence in the red chalk of Yorkshire is noticed in the 'Geologist,' 1859, p. 275 ; and 

 I860, p. 420. 



Pig. 3. Textularia trochus, jy Orbigny. 



One of the most symmetrical of the Textularife,* and found chiefly in the Chalk, ac- 

 companied with T. turris and many other varieties. 



Pig. 4, 5. Textularia agglutinans, Orbigny, var. 



The Textularise are so variable in their growth, forming vesicular or flattened cham- 

 bers, and arranging them sometimes so regularly and at other times with such a want 

 of neatness, that there may be almost as many names for them as there are individuals. 

 Fig. 4 and 5 are examples of this. Badly grown specimens of the typical form known 

 as T. agglutinins, they form links w r ith the variety named T. fteda and many others. 

 These Textularise are extremely common in the Gault, Chalk-marl, and Chalk. 



Fig. 6. Textularia Baudouineana, D" Orbigny. 



This is another common form of Textularia, more symmetrical in outline and in the 

 setting on of its compressed chambers, than Fig. 4 and 5. It can be scarcely, if at all, 

 distinguished from a well-grown T. sagittula, Defrance. 



Pig. 7, 8. Planorbulina ammonoides, Beuss, sp. 



Most of the Planorbulinse, especially the larger forms, live in the shallower sea-zones, 

 chiefly among seaweeds ; but in deep water they pass into smaller and more compact 

 varieties, such as Fig. 7' and 8. These subnautiloid forms are common in some of the 

 Jurassic clays and in the Gault, Chalk-marl, and Chalk, and abound in the existing seas 

 at depths greater than 100 fathoms. 



Pig. 9-11. Pultinulina| umbtlicata, D' 'Orbigny, sp. 



This belongs to a large family of Rotaline Foraminifera, which group themselves 

 around Pulvinulina repanda, Fichtel and Moll., sp. It belongs more especially to the 

 subgroup of which P. Menardii is the type. This attains its best growth at about 100 

 fathoms in the existing seas, but lives well at abyssal depths, even at more than two 

 miles depth ; whilst, on the contrary, in shallow water it degenerates into bizarre varie- 

 ties. D'Orbigny's Rotalia Micheliana and R. crassa, figured on the same plate (Mem. 

 Soc. Geol. France, iv. pi. 3) from which Fig. 9-11 have been copied, are also varieties 

 of Pulvinulina Menardii. These are all three found in existing seas under the condi- 

 tions mentioned above, and are abundant in the Gault, Chalk-marl, and Chalk. 



Pig. 12. Lituola nautiloidea, Lamarck. 



This is the elongate form of Lituola, the short condition of which is more or less nau- 

 tiloid in shape. Lituola has very variable states of growth according to its place of 

 living, and is often attached to shells, seaweeds, etc. ; it has therefore many varieties, re- 

 cent and fossil. 



Pig. 13. Marginulifa trilobata, D' Orbigny. 



Marginulinaj are Cristellariaj with short chambers, arranged without coiliug, except 

 at the commencement. They are present wherever Cristellarirc abound. 



Pig. 14, 15. LisrGULitfA CARINATA, D' Orbigny. 



This is a smooth compressed Nodosaria, the gradation from cylindrical to flattened 

 forms being extremely gentle in numerous intermediate forms ; and further, these flattened 

 Nodosarite, by the backward growth of the sides of the chambers and further compression, 

 gradually pass into Froudicularia ; see "Quart. Journ. Geol. Soc. xvi. p. 453, pi. 19. 

 Lingulinse are not very common in the Cretaceous formations. The specimen figured 

 (Pi. XV., Fig. 14, 15) is a remarkably fine individual (magnified six times) from the Chalk 

 of Gravesend. Fig. 14 shows the slit-like aperture. 



* See "Memoir on Textularise," by Messrs. Parker and Jones, Annals of Nat. Hist. 

 February 1803. 



f For the description of t he genera Pulvinulina and Planorbulina, see Carpenter's 

 * Introduction to the Study of Foraminifera' (Ray Society), 1862, p. 200, 210, etc. 



