On the Nomenclature of the Foraminifera. 91 



Addendum. 



9. Spiraxis Cingalensis, B., n. sp. 



5. testa subrimata, subulato-turrita, gracili, solida, polita, striatula, 

 striis minutis confertissimis uudulatis spiralibus decussata; spira 



elongata, superne sensim attenuata, apice ? sutura vix im- 



pressa, irregulari ; anfractibus superstitibus 1 1 (apicalibus defi- 

 cientibus), planulatis, ultimo ad basin rotundato ; apertura sub- 

 obliqua, emarginato-elliptica ; peristoraate recto, intus ad angulum 

 superiorem calloso ; margine dextro supeme arcuato, basali incras- 

 sato, columellari calloso, expansiusculo, subreflexo, superne plica 

 obliqua spirali solida munito. 



Long. 14, diam. 3 mUl. ; apert. long. 3, diam. 1|^ mill. 



Habitat ad Weelgamoowe, Matelle, Ceylon. 



A single specimen of this peculiar form is in Mr. F. Layard's 

 collection. It is a dead shell, and is deficient in the superior 

 whorls. I had not seen it before the previous part of this paper 

 was in type. 



January 8. 



XIII. — On the Nomenclature of the Foraminifera. 

 By W. K. Pakker, M. Micr. See., and T. E. Jones, F.G.S. 



Part Ylll.—Textularia. 



As the typical Bulimina have a strong resemblance externally to 

 a Bulimus, so the large Textularia trochus, D'Orb., insensibly 

 losing itself in T. turris, D'Orb., brings to mind the shape of 

 the Trochus among Mollusca. The mimetic T. trochus, however, 

 can scarcely be considered as the t}^e of this very variable spe- 

 cies ; for the circularity of the transverse section or of the base 

 of the cone is rather to be regarded as an extreme condition, — 

 the conical forms of Textularia being homomorphous with the 

 short forms of Bulimina variabilis and the broadly conical poly- 

 stomous Valvulina. 



Textularia agglutinans, D^Orb., oval in its transverse section, 

 and with more or less irregular gibbosity of its chambers, gives, 

 in its ordinary and moderately developed condition, a fuller idea 

 of the species than any other variety. The T. sagittula of De- 

 france was the first to receive the generic name. It is smaller 

 than the foregoing, and more compressed, and leads down to the 

 most delicate variety, T.pygmaa, D'Orb. It does not present the 

 mean of the specific characters, however, and thus does not 

 supply a fair type of the species. 



Among the very minute organisms to be seen in marine de- 

 posits, recent and fossil (such as chalk-dust and the mud of the 

 Clam-beds of the East Indies), are tinv, delicate, translucent 



7* 



