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tertiaries. These two orders join very near the base, each pair 
of tertiaries curving and meeting the enclosed straight secondary. 
The intercostal spaces are narrower than the cost, and are 
crossed by slender transverse bars, between which a series of 
longitudinal openings or pores penetrate the wall. Towards the 
base of the corallum the pores become very small and barely dis- 
tinguishable. 
Height of corallum, 5 mm.; length of calice, 3mm.; breadth 
of calice, 2 mm. 
Localities—Upper Eocene, Spring Creek (type); Middle 
Eocene, Muddy Creek. 
Trematotrochus lateroplenus, spec. nov. Pl. ix., figs. 2a, b. 
Corallum much like the preceding, but less compressed 
inferiorly. It is subcylindrical for a short distance from the base, 
and then expands so as to form a flattish cone with rounded 
lateral borders. Calice elliptical and shallow ; its axes are in 
the ratio of 100 to 62. 
Septa in six systems with four cycles, but the fourth cycle is 
developed only in the end systems which are correspondingly 
larger than those at the centre. Asin TZ. complanatus, the six 
primaries are very stout, and rise above the general level of the 
calice. The secondaries and tertiaries are equal, and compara- 
tively slender, while the quaternaries are, as a rule, smaller still. 
The latter are usually free, and the primaries uniformly so, but 
the secondaries and tertiaries in the lateral, and occasionally also 
in the central systems, are irregularly fused together close to the 
columella. The sides of all the septa are studded with sharply 
pointed granules, and their upper margins have consequently a 
dentate appearance. Some infilling of the interseptal spaces is 
due, I think, to the development of stereoplasma and not to true 
endotheca. 
Columella elongate, irregular in outline, and tending to spread 
laterally in the fossa. Its upper surface is nodular, papillary, or 
even spongy in texture. It is fused, either directly or by means 
of thin processes, with the inner margins of the primary, 
secondary, and occasionally the tertiary septa. 
Costz broad, flat, and continuous with the septa. They are 
evenly placed round the border of the calice, the greater marginal 
extent of the four end systems giving room for the extra cycle of 
costz developed in them. The base of the corallum is formed by 
the union of twelve coste, of which the six primaries remain free 
to the summit. The secondaries are joined at a short distance 
from the base by the tertiaries, and these again in the lateral 
systems by the slightly shorter quaternaries. The intercostal 
spaces are,narrow and regularly porous in the manner charac- 
teristic of the genus. 
