TRIGONTA, 
~I 
je) 
and hinge-area; it is therefore possible that this form may belong to Pectun- 
culus. 
Distribution —Chalk Rock (zone of Heteroceras Reussianwir) of Cuckhamsley. 
Family—TRIGONIIDAS, Lamarck. 
Genus—Triconia, Bruguiere, 1789. 
(‘Encye. Méth. Vers.,’ vol. i, p. xiv; Lamarck, ‘ Syst. Anim. sans Vert.,’ 1801, p. 116.) 
The British forms of this genus have already been considered in detail by Mr. Lycett in his 
‘Monograph of the British Fossil Trigoniw,’ published by the Palaontographical Society in 1872-9 ; 
it will therefore not be necessary, in the present work, to do more than enumerate the Cretaceous 
species, and to give some additional notes on their affinities, synonymy, etc. 
Section 1.—ScAPHOIDES. 
TRIGONIA SCAPHA, Agassiz, 1840. Plate XX, figs. 1, 2. 
Additional Synonymy. 
1861. Triconta HuNsTANTONENSIs, H. Seeley. Ann. Mag. Nat. Hist., ser. 3, 
vol. vii, p. 123, pl. vi, fig. 9. 
1877. — scapHa, Lycett, p. 183, pl. xxxviil, fig. 6. 
1884. — —- O. Weerth. Die Fauna Neocom. im Teutoburg. Walde 
(Palxont. Abhandl., vol. ii), p. 45. 
1896. — — A. Wollemann. Zeitschr. d. deutschr. geol. Gesellsch., 
vol. xlvili, p. 846. 
1900. —- — _- Die Biv. u. Gastrop. d. deutsch. u. 
hollind. Neocoms. (Abhandl. d. k. 
preussisch. geol. Land, N. F., 
pt. 31), p. 92. 
(iii) Z. radiata. Alth, ibid., p. 284, pl. xii, fig. 19; Favre, ibid., p. 122, pl. mii, fig. 18. 
(iv) LZ. plana. Romer, ‘ Die Verstein. des norddeutsch. Kreidegeb.’ (1841), p. 69, pl. vill, fig. 24 ; 
Griepenkerl, “Senon. Kreide von Kénigslutter,’’ ‘ Paleont. Abhandl.,’ vol. iv (1889), p. 56. In this 
form the valves appear to be flatter and the umbones less prominent than in the English species 
described above. 
(v) Pectunculus? insculptus, Reuss, ‘ Die Verstein. der bohm. Kreideformat.,’ pt. ii (1846), p. 8, 
pl. xxxv, fig. 5; Fritsch, ‘Stud. im Gebiete der bohm. Kreideformat., vy. Priesener Schichten’ (18938), 
p. 98, fig. 106, 
10 
