400 PLIOCENE MOLLUSCA. 



trigonal, angulated by the keel; outer lip crenulated, grooved within; umbilicus 

 well marked, but not so large or deep as in T. u-mbilicare ; peristome continuous; 

 columella triplicate. 



Dimensions. — L. 25 — 30 mm. B. 18 — 22 mm. 



Distribution. — Not known living. 



Fossil; Scaldisien : Belgium. 



Miocene : France, Belgium, Germany, Vienna basin, Italy. 



Lower Pliocene : Italy. Upper Pliocene : Italy, Sicily. 



Remarks. — The generic (or sub-generic) name Trigonostoma is used for a 

 scalaroid group of the Cancellariidae having a sub-triangular mouth without a 

 distinct canal, a deep umbilicus and a columella deviating upwards towards the 

 axis of the shell, further characteristics of which have been more fully given by 

 M. Cossmann (op. cit., vol. iii, p. 24). 



T. ampullaceum occurs in the Italian Pliocene, somewhat rarely in the Lower 

 or Piacenziano deposits, but more abundantly in the Astiano. The type form has 

 not been definitely recorded from the English Crag, l but one of the two specimens 

 figured by Nyst in 1881 from the Belgian Scaldisien as T. umbilicare (pp. cit., pi. 

 xxviii, fig. 8) may represent the present species, T. ampullaceum ; the other 

 (pi. i, fig. 5), being a typical example of T. umbilicare. As the two forms are similar 

 in some respects, I have figured for the guidance of students a verified specimen of 

 T. ampullaceum (PI. XL, fig. 1) from Asti that I have received from my friend 

 Prof. Sacco of Turin; this compared with a figure of T. umbilicare on the same 

 plate (fig. 3), also from Asti, will show the difference between the two species. 



M. Van den Broeck reports T. ampullae cam from the Belgian Miocene 

 (Bolderien), and it occurs in deposits of similar age in other parts of Europe. As 

 it seems to have been found by Nyst in the Scaldisien of Belgium, there is no 

 reason why it should not be obtained hereafter from the English Crag. 



Trigonostoma umbilicare (Brocchi). Plate XL, figs. 3, 4. 



1814. Voluta umbilicarls, Brocchi, Couch, foss. subap., vol. ii, pp. 312, 645, pi. iii, figs. 10, 11. 

 1826. Cancellaria umbilicaris, Risso, Hist. nat. Eur. merid., vol. iv, p. 187, no. 481. 

 1841. Cancellaria umbilicaris, Bellardi, Desc. Couch, foss. Piem., p. 35, pi. iv, figs. 17, 18. 

 1843-81. Cancellaria umbilicaris, Nyst. Coq. foss. Belg., p. 482, pi. xxxix, fig. 16, 1843 ; Couch. Terr. 



tert. Belg., p. 8, pi. i, fig. 5, 1881. 

 1872. Cancellaria umbilicaris, d'Ancoua, Mem. Cart. Geol. Ital., vol. ii, p. 209, pi. xiii, fig. 10. 

 1874. Cancellaria umbilicaris, S. V. Wood, Mou. Crag Moll., 1st Snppl., pt. ii, p. 182, Add. pi., 



fig. 10. 

 1874-92. Cancellaria umbilicaris, Van deu Broeck, Ami. Soc. Roy. Malac. Belg., vol. ix, p. 272, 1874 ; 



Bull. Soc. Beige Geol., vol. vi (Memoires), p. 131, 1892. 



1 I have au imperfect and fragmentary specimen from Oakley which may possibly belong to this 

 species. 



