78 CRETACEOUS LAMELLIBRANCHIA. 
TRIGONIA DUNSCOMBENSIS, Ivycett, 1877. Plate XIX, figs. 12 a, b. 
e co} 
1877. Lycett, p. 188, pl. xl, figs. 5, 6; pl. xh, fig. 14. 
1896. A. J. Jukes-Browne and W. Hill. Quart. Journ. Geol. Soc., vol. lii, p. 153. 
Remarks.—Messrs. Jukes-Browne and Hill consider that 7. dunscombensis is 
probably identical with 7. sinwata, @Orbigny (non Parkinson) which I regard 
as a synonym of 1’ affinis (see p. 77). Small forms (85 mm. long) seem to be 
inseparable, unless it is by the somewhat greater convexity of 7. dunscombensis, 
but the larger examples of the latter (e.g. Lycett’s fig. 5) seem to differ in having 
a less ovoid outline and fewer ribs. More specimens of 7’. duiscombensis are 
needed before its affinities can be definitely settled. 
Types.—Figs. 5 and 6, from near Sidmouth, are in Mr. Meyer's collection. The 
original of pl. xh, fig. 14, from Dunscombe, is in the Museum of Practical 
Geology. 
Distribution—Cenomanian (Beds 10, 11, and 12 of Meyer) of Dunscombe, 
Branscombe, Whitecliff, and Pinhay; Bed 11 of Humble Point, Lyme Regis. 
Base of Chalk Marl (zone of Schlaenbachia varians) of Titherleigh. 
TRIGONIA DEBILIS, Lycett, 1877. 
1877. Lycett, p. 189, pl. xl, fig. 8; pl. xi, fig. 5. 
1896. A.J. Jukes-Browne and W. Hill. Quart. Journ. Geol. Soc., vol. li, p. 154. 
Types.—In Mr. Me¥er’s collection (fig. 8), and in the Museum of Practical 
Geology (fig. 5). 
Distribution —Cenomanian (Bed 10) of Dunscombe. 
Section 4.—QUADRATR. 
TRIGONIA NoposA, Sowerby, 1826. 
oy J? 
1822. TrRIGoNIA CLAVELLATA, G. Mantell (non Sowerby). Foss. 8. Downs, p. 73. 
1826. _ noposa, J. de OC. Sowerby. Min. Conch., vol. vi, p. 7, pl. dvi, 
fiom, 
P1840. — crnora, L. Agassiz. Etudes crit. Moll. Foss. (Trigon.), p. 27, 
pl. vii, figs. 21, 28; pl. viii, figs. 2—4. 
1844, — rupIs, A. d’Orbigny. Pal. Frang. Terr. Crét., vol. ii, p. 187, 
pl. eelxxxix, 
