(U PLIOCENE MOLLUSCA. 



Some of the fossils from the Isle of Man figured by Prof. Kendall and by Mr. 

 Lamplugli as N. serrata seem to be the present variety. Prof. Kendall's fig. 1 

 corresponds with my var. lineata (PI. Ill, f]g. 18). 



Var. incisa, nov. Plate III, fig. 4. 



Dimensions. — L. 36 mm. B. 20 mm. 



Dhfrihiition. — Not known living. 



Fossil : Waltonian Crag : Little Oakley. 



Bemarlcs.^As far as my experience goes, and with one exception, the spiral 

 sculpture of the shells grouped by "Wood as -A^. reticosa consists of raised lines or 

 bands more or less distinct or prominent. In the variety tiara, however, it takes 

 the form of rather faintly impressed or incised striae. I have a specimen from 

 Oakley which corresponds with the latter in this respect, but the whorls are 

 regularly rounded and convex, and not angulated below the suture. To some 

 extent our fossil approaches one or two varieties of the Mediterranean species N. 

 imitahilis figured by Kobelt (Icon, schalentrag. europ. Meeresconch., vol. i, p. 122, 

 pi. xxi, figs. 20, 21, 1887). 



The fact that the spiral sculpture of all the specimens of N. reticosa known to 

 me, except those of the present one and the variety tiara, consists of raised and 

 not of grooved lines, suggests that these forms may possibly belong to a separate 

 species. 



Nassa semireticosa, Etheridge and A. Bell. Plate III, fig. 11. 



1885. Nassa serrata, S. V. Wood, Quart. Jourii. Geol. Soc, vol. xli, p. 65. 



1886. Nassa serrata, Kendall and R. Gr. Bell, Quart. Journ. Geol. Soc, vol. xlii, p. 201. 

 1890. Nassa serrata, C. Eeid, Plioc. Dep. Brit., p. 63. 



1893. Nassa serrata, A. Bell, Proc. Roy. Irish Acad. [3], vol. ii, p. 626. 



1898. Nassa semireticosa, Etheridge and A. Bell, Trans. Roy. Geol. Soc. Cornwall, vol. xii, p. 140, 

 pi. i, fig. 7. 



Specific Characters. — Shell generally thick and solid, varying greatly in size ; 

 whorls but little convex, slightly depressed below the suture ; ornamented by strong- 

 longitudinal ribs, rather oblique, especially on the last whorl, crossed by spiral 

 costge which become tuberculate at the point of intersection ; suture deep, 

 channelled ; mouth ovate, acutely angulate above ; outer lip but little expanded, 

 thickened internally and grooved in correspondence with the spiral costation ; canal 

 notched, wide and very short, opening to the left. 



Dimensions. — L. 18 — 40 mm. B. 10 — 20 mm. 



DistrUmtion. — Not known living. 



Fossil : Pliocene deposits : St. Erth. 



