Mr. II. J. Carter on the Fossil Foraminifera of Scindo. 381 



viety in the same species, and of the difficulty of determining 

 which are species and which varieties. 



The internal structure of Alveolina elliptica is exactly that of 

 Nummulites elongated vertically, with the exception of the layers 

 of spicules of which the spicular cord is composed in the latter 

 being separated into ridges in the former, and the septal divi- 

 sions, instead of stopping at the spicular cord, being carried 

 through it, in Alveolina, while the intervals between the ridges 

 appear to correspond to the layers of anastomosing canals or 

 marginal plexus in the cord of Nummulites. I have never been 

 able to see any traces of spicules or of a marginal plexus in the 

 marginal or canaliferous layer, as it may be termed, of Alveolina ; 

 but then I have never yet met with any richly infiltrated specimens 

 to enable me to determine this, as in Nummulites. Tracing the 

 transition still further, in proportion as a Nummulite becomes 

 thick the external turns of the spire are more approximated, until, 

 in the globose forms, they are almost as much in contact as in 

 Alveolina, that is to say, there is hardly any space for chambers 

 left; hence their approximation becomes greatly increased when 

 the globose passes into the elliptical form, as in Alveolina, where 

 there is no space at all left for the chambers ; while the turns of 

 the canaliferous layer which correspond, as before stated, to the 

 spicular cord of Nummulites, are thus brought into direct contact 

 with each other. But this approximation, although chiefly oc- 

 curring in the outermost layers in Alveolina, is not always con- 

 fined to them, as it sometimes commences from the first cell and 

 is continued throughout, while in others it begins with the spire, 

 and ceasing after two or three turns, is followed by a turn or 

 two of chambers, and then again the canaliferous layers become 

 approximated. So one might fairly infer that the functions of 

 the soft structures of the canaliferous layer and that of the soft 

 structures filling the chambers were different ; for it is evident 

 that the former went on growing without the presence of the 

 latter (and, indeed, it would be difficult to make out any cham- 

 bers in many of the globose forms of N. perforata towards the 

 circumference) ; but the chambers do not appear, in like manner, 

 without the presence of the canaliferous layer. Hence, as before 

 stated, may we not infer that the latter contains the developing 

 part of the organism, and the former the reproductive one ? 



Alveolina meandrina, n. sp. (PI. XVII. fig. 4, &c). — Elliptical, 

 nearly globular, externally covered with whorls of tortuous septal 

 lines and interspaces, indicating the form of the chambers be- 

 neath ; internally composed of a spiral layer of long, narrow, 

 tortuous chambers commencing from a central cell and gradually 

 elongating themselves in each direction, at right angles to the 

 spire, as the latter winds round its long axis to form the test, 



