161 



LXXXVI. Lenticulina. A sublenticular, multilocular, spiral univalve ; 

 the external margin of the turns being complicated, the septa reaching 

 to the centre on each side : the , septa entire, curved, and standing out, 

 on the upper and under surface, like rays. The aperture narrow, and 

 projecting beyond the penultimate turn. 



These shells are distinguished by Lamarck from those of Nautilus, by 

 their having no syphon ; and from those of Discorbis and Rotalites, by 

 the septa reaching to the centre on each side. He states, that the 

 recent shell has been found in the .sea, near Teneriffe, at the depth of a 

 hundred and twenty-five feet. Three species are found fossil in the 

 environs of Paris : L. planulata, L. variolaria, and L. rotulata. The last 

 of these I have represented from Lamarck, Plate XI. Fig. 4, being 

 entirely unacquainted with this genus. 



LXXXVII. Lituola. A multilocular univalve, partly spiral, the last 

 turn being straight at the end : the chambers irregular : plain transverse 

 septa, the last having several openings. 



The chambers of this shell appear to be very irregularly disposed, and 

 the orifices in the last septum are generally from three to six; but the 

 other septa do not appear to be pierced by any siphunculus. 



Lamarck describes two species, both fossil, not knowing of their exist- 

 ence in a recent state. Plate X I. Fig. 5, is a representation of Lituo- 

 lites nautiloidea. Fig. 6, is L. difformis ; and Fig. 7> is the same shell, 

 rubbed down, to show the internal structure. 



I have suspected the former of these shells to be, perhaps, N. semi- 

 lituus, or subarcuatulus, and the latter to be N. carinatulus, Fig. 73, of 

 Walker ; but there is no agreement in the openings. 



LXXXVIII. Spirolina. A multilocular univalve, in part spirally con- 

 voluted : the turns contiguous, the latter ones straight : the septa trans- 

 verse, perforated by a tube. 



These minute shells are so alike in their general form to those of the 

 genus Spirula, that Lamarck, who has discovered several species and 



VOL. III. ' Y 



