PLATE 28 A. 
fage 
Fig. 1 a - h. Trematospira camura (of the Niagara group). 212 
1 a. Dorsal view of a specimen of medium size. 
1 b. Ventral view of the same, showing a single small plication in the mesial sinus. 
1 b f. Ventral view of a specimen somewhat different in form. 
1 d. Profile view of the same. 
1 e. Enlargement of the beak, foramen and deltidium of the ventral valve, and the upper part 
of the dorsal valve. 
1 /. Dorsal view of a shorter specimen, which has been cut transversely to show the internal 
spires. 
1 g. Enlargement of plications, showing granulose surface and strong imbricating lines of 
growth. 
1 h. Surface of plications enlarged, showing granulose surface without imbricating lines of 
growth. 
Fig. 2 a - f. Trematospira simplex. 211 
2 a, b. Dorsal and ventral views of the specimen, natural size. 
2 c, d. Front and profile view of the same. 
2 e, f. Dorsal and ventral views of a larger specimen, the lateral extremities of which are 
broken off. 
Fig. 3 a - k. Trematospira perforata. 208 
3 a. Dorsal view of a small specimen. 
3 b, c, d. Dorsal, ventral, and profile views. 
3 e,f. Dorsal and ventral views of an older specimen with a deep sinus. 
3 g, h. Front views of a young and an old specimen, showing the shallow and deeper mesial 
sinus. 
3 i. Ventral side of an imperfect specimen, showing the internal spire. 
3 fc. Eidargement showing the perforated beak and the junction of the valves. 
Fig. 4 a - e. Trematospira costata. 
4 a, b. Dorsal and ventral valves. 
4 c, d. Profile and front views. 
4 e. Enlargement of the surface, showing the granulose punctate character, which is obscure 
from the silicification of the shell. 
210 
Fig. 5 a - f. Trematospira mttltistriata. 209 
5 a. An individual of medium size, having the beaks closely incurved, and without indication 
of an area. 
5 b. Dorsal view, where the minute perforation in the beak of the ventral valve is barely seen 
above the summit of the opposite one. 
5 c, d, e. Ventral, front, and profile views of the same individual. 
5/. The interior of a ventral valve, showing the remains of internal spires. 
