On Gycloloculina. 535 



Rotalinse of Brady's ninth family, the Eotaliidre, and between the 

 genera Discorbina and Planorbulina, which are its nearest allies, 

 although the absence of special aperture might lead one to suppose 

 that its affinities were with the Tinoporinae. The earliest chambers 

 however, which are on the Discorbine plan of growth, mark its affinity 

 to that genus. It differs from Planorbulina, to which it bears a 

 superficial resemblance externally, in the construction and arrange- 

 ment of its later chambers, and in the absence of definite oral 

 apertures. In Planorbulina the chambers succeeding the early 

 spiral portion are arranged in more or less concentric order, but the 

 method of arrangement rapidly becomes obscure, and one portion 

 of the periphery often grows more rapidly than another, owing to 

 the accretion of chamberlets. Planorbulina, moreover, is more or 

 less an adherent form, and the later chambers grow to some extent 

 over their predecessors, so that the initial spiral portion is only 

 visible on the under, or attached, surface of the test. This over- 

 lapping reaches its fullest development in P. accrvalis (Brady), in 

 which the chamberlets are irregularly heaped together. 



In Planorbulina, moreover, the oral apertures are very well 

 defined, consisting of minute arched slits, with everted lip, placed 



A 



/""V- 



4^y\ 



stfpzz&r. 



Fig. 138. — Diagrammatic Section of a Portion of Planorbulina. 



A, oral apertures. 



on each side of the chamberlet at the* points of attachment co the 

 previous whorl. 



Our type bears a somewhat superficial resemblance to a species 

 which was described by d'Orbigny under the name of Planorbulina 

 >•< rmiculata, but which was transferred by Brady to the genus 

 Pulvinulina on grounds which do not appear very convincing to 

 us. It may be noted that Brady assigns Terquern's Planorbulina 

 Eocccna to this species, but we think incorrectly, as specimens 

 which are undoubtedly referable to Terquern's species are of 

 frequent occurrence at Bognor and Selsey, and they bear but little 

 resemblance to Pulvinulina {Planorbulina) vermiculata, of which 

 we have excellent specimens from the Mediterranean. 



The undivided tubular chambers which are the characteristic 

 feature of the genus Cycloloculina, have no parallel in the 

 Foraminifera. D'Orbigny 's second order, the Cyclostega, was 



