THE FAMILY LITUOLlDiE 139 



specific characters with any form of the same genus 

 now fomid hving. (Plate 7, fig. C.) 



H. nomoninoideSj Reuss, ' Sitzungsb. k. Ak. Wiss. 

 Wien,' vol. xlvi. 1862, p. 30, pi. i. fig. 8. 



The test of this fossil form is composed of sand- 

 particles of medium coarseness, of a pale grey to a 

 ruddy brown colour, w^ith occasional chips of green 

 glauconite interspersed. The contour of the shell is 

 well rounded and fairly subgiobular in form, but 

 flattened at the umbilici. The arched slitlike aper- 

 ture is very nearly central on the septal face of the 

 shell. As to distribution in geological time, it is 

 quite a restricted form ; for it first appears in the 

 Aptian formation of England and afterwards in the 

 Gault both of England and Germany. (Plate 7, 

 fig. D.) 



Genus Placopsilina, D'Oebigny. 



Chambers plano-convex, adherent. Jurassic to 

 Beceiit. 



Example. — P. cenojnana, D'Orbigny, ' Prodrome 

 Paleont.' vol. ii. 1850, p. 185, No. 758 ; Eeuss, 

 'Denkschr. k. Akad. Wiss. Wien,' vol. vii. 1854, 

 p. 71, pi. xxviii. figs. 4, 5. 



Some of the modifications of this species consist 

 of a long sinuous series of adherent segments, whilst 

 some allied forms are monothalamous. The figure 

 given here is from an intermediate type of shell, and 

 appears to be constructed chiefly of coral sand. The 

 test is usually seen wdth a spiral commencement, 

 afterwards running off into a linear series. Some of 



