166 Mr. H. J, Carter on Fossil Foraminifera in Scinde, 



Orbitoides, of which Lycojihris dispansus is a type, it is evident 

 that it is not the case, but that the chambers are arranged sub- 

 spirally. 



That Orbitoides Mantelli should be included among the Orbi- 

 tolites and not among the Orbitoides, must also now be evident, 

 from the striking differences that exist between it and Lycophris 

 dispansus, and its identity in structure with Orbitolites generally ; 

 while the intervening link between it and Nummulina is natu- 

 rally supplied by Orbitoides bearing the characters above men- 

 tioned. It may be observed, that the cells of the central plane 

 in O. Mantelli are elongated and not spheroidal, but the one 

 seems to be as constant as the other, and the elongation verti- 

 cally only to depend, as before stated, on the thinness above and 

 below of the walls of the cells forming the central plane, which 

 renders those parts imperfect or imperceptible in the vertical 

 section, and makes the cells appear to run into one another ; 

 while the opake material or intercellular substance showing out 

 at their sides, gives them that septal and at the same time qua- 

 drangular form, which approximates the whole central plane in 

 appearance to that seen in the vertical section of Orbitoides and 

 Nummulina. 



There are several other observations which I have to make on 

 the structure of these two genera, but they will be better under- 

 stood in connection with their species when respectively de- 

 scribed. 



As the list of synonyms of the discoidal Foraminifera already 

 described is very great, for the short time they have become in- 

 teresting*, at the same time that their descriptions are very few 

 and not within my reach, I shall avoid as much as possible 

 introducing new names here, in hope that others who are more 

 favourably situated may be able to do this from my descriptions 

 and figures, if required, or that I may be able to do it myself at 

 some future period, when I have better means of comparing the 

 specimens of different localities than I at present possess. Mean- 

 while, as so little has been done in the subject, I am not without 

 hope that that which I have now to offer may be found useful. 



In order of description I shall not exactly follow D^Orbigny's 

 arrangement, that I may be the better able to show the trans- 

 ition from the simple to the more complicated forms of discoidal 

 Foraminifera. Thus, I shall place Operculina before Nummulina, 

 &c. ; Alveolina after A^. obtusa, Sowerby, and before N. acuta, id. ; 

 and then pass on to Orbitoides and Orbitolites. 



The figures in the Plate are intended to represent the largest 



* See Murchison on the Structure of the Alps (Quart. Journ. Geol. Soc. 

 vol. V. p. 309). 



