TRIGONOSTOMA (VENTRIUA) ACUTANGUIJM. 401 



1876. Cancellaria umbilicaris, Seguenza, Boll. R. Com. Geol. Ital., vol. vii, p. 8, no. 449. 

 1878. Trigonostoma umbilicaris, de Stefani e Pantanelli, Bull. Soc. Malac. Ital., vol. iv, p. 115. 

 1890—4. Cancellaria umbilicaris and vars., Sacco, Boll. Soc. Geol. Ital., vol. ix, p. 264, no. 3865, 1890 ; 



C. (Trigonostoma) umbilicare and vars., Moll. Terr. Terz. Piem., pt. xvi, p. 4, pi. i, figs. 4 — 6, 1894. 

 1896. Cancellaria umbilicaris, Bernays, Bull. Soc. Beige Geol., vol. x (Memoires), p. 131. 

 1899. Trigonostoma umbilicaris, Cossmann, Ess. Paleoconch. couipar., vol. iii, p. '25, pi. ii, figs. 1, 2. 

 1912. Cancellaria umbilicaris, Tesch, Med. v. d. Rijks. v. Delfstoffeu, no. 4, p. 86, no. 216. 



Specific Characters. — Shell strongly and deeply umbilicate ; whorls scalariform, 

 compressed below, deeply excavated above with a concave shelf below the suture, 

 crossed obliquely by the ribs ; the last ventricose, much the largest ; ornamented 

 by oblique or flexuous longitudinal costse, ending in more or less clearly-marked, 

 recurved spines and crossed by spiral ridges ; spire short, rapidly diminishing in 

 size upwards, ending in a blunt point; mouth triangular; peristome continuous; 

 umbilicus wide, deep and open, extending to the upper end of the spire; columella 

 with two strong folds and a smaller one below. 



Dimensions. — Of the Crag specimen, L. 22 mm. B. 15 mm. 



Distribution. — Not known living. 



Fossil: Newbournian Crag: Waldringfield. 



Scaldisien : Antwerp, Dutch borings. 



Italian Pliocene: Piacenziano (rare). Astiano : Asti (abundant). Sicily — 

 Altavilla. 



Remarks. — This species, which is exceedingly common in the Upper Pliocene 

 at Asti where I found one of the specimens here figured, may be distinguished 

 from the one last described by its open and deep umbilicus which penetrates to 

 the apical end of the spire. Except that the Crag specimen, which is from the 

 Canham collection in the Ipswich Museum, is rather shorter than the Asti fossil, 

 it corresponds very closely with it. The former is but little worn, and as 

 T. umbilicare is characteristic of the Upper Pliocene of Italy there seems no 

 necessity for regarding it as derivative in the Crag. Dr. Tesch informs me, 

 moreover, that he has obtained 5 typical examples of it from beds he regards as 

 Scaldisien in a boring at Grave-Oss in North Brabant, and M. Bernays reports it 

 from deposits of similar age at Antwerp. The fossil from Waldringfield figured 

 by Wood {op. cit.) is, I consider, the true T. umbilicare. 



Sub-genus VENTRILIA, Jousseaume, 1888. 

 Trigonostoma (Ventrilia) acutangulum (Faujas-de-Saint-Fond). Plate XL, fig. 2. 



1817. Cancellaria acutangula, Faujas-de-Saint-Fond, Mem. Mus. Hist. Nat. Bordeaux, vol. iii, pi. x, 



fig. 1. 

 1825. Cancellaria acutangula, Basterot, Mem. Soc. Hist. Nat. Paris, vol. ii. p 45, pi. ii, fig. 4. 



