PHOSPHATIC CHALK OF TAPLOW. 515 



irregularly pitted. Length -^ in. (0*42 millim.). Two specimens 

 only were found. 



(ii) Textularia decurrens, sp. nov. PI. XY. fig. 6. 



Amongst a large number of the globulose-cliambered Textularim 

 so abundant in the Taplow Chalk were noticed several specimens 

 more or less inclined to depart, in the latest growth of the shell, 

 from the bi-serial or Textularian type and to become spirally uni- 

 serial, showing in fact the reverse of the essential character of the 

 genus Spiroplecta. The specimen figured represents this abnormal 

 growth in perhaps its best development. It is only another instance 

 of the readiness with which a form will depart from its type, 

 serving perhaps as a link not only between species, but it may 

 be between genera also. Length -^-^ in. (0*56 millim.). 



(iii) Textularia serrata^ sp. nov. PI. XY. fig. 7. 



This is a somewhat elongate form resembling, by the hollowed 

 faces of the shell, T. concava of Karrer ; but the species is distinctly 

 separable from the latter by the attenuated form and the constric- 

 tions between the pairs of chambers. T. serrata generally possesses 

 a single terminal chamber, probably an indication of age ; and in 

 some specimens a slit-like aperture can be seen disposed horizontally 

 at its base. Length -j^ in. (0*56 millim.). Common in the Tap- 

 low Chalk. 



(iv) Bulimina trigona, sp. nov. PI. XV. fig. 8. 



Test subconical, three-sided, slightly twisted, and with the 

 aboral end thickly granulated, or studded with short prickles. 

 This form resembles one variety of B. elegans in the three-sided dis- 

 position of the series of segments, but is much stouter and more 

 angular. Length -^ in. (0*5 millim.). Preauent in the Taplow 

 Chalk. 



(v) Bolivina strigillata, sp. nov. PL XV. fig. 10. 



*.■ 



Test compressed, triangular, and elongate, tapering gradually to 

 the commencement of the shell. The surface of the test bears 

 oblique raised ridges, sometimes broken into tubercles. The orna- 

 mentation of the shell somewhat resembles that of B, decorata, 

 Jones, recorded by Mr. Joseph Wright, F.G.S., from the Chalk of 

 Keady Hill, in the North of Ireland,^ but differs from the latter in 

 .the lengthened, rather than dilated, form of the shell. Length 

 ^ in. (0-63 millim.). Common in the Taplow Chalk. 



1 Proc. Belfast Nat. Field Olub, Appendix ix. (1884-85), p. 330. 



