318 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
We are able to distinguish the principal genera only by the nature of their 
frontal. 
Following the Membraniporae, these are the most ancient Cheilostome fossils 
known. 
Genus ACROPORA Reuss, 1869. 
1869. Acropora Reuss, Die fossilen Anthozoen und Bryozoen der Schichtengruppe von 
Crosaro, Denkschriften der k. Akademie der Wissensehaften, Wien, vol. 29, p. 277. 
The zoarium is free and escharian. The frontal is a thick tremocvst with 
tubules. The avicularia are grouped on the peristome. 
Genotypes.— Acropora ( Eschara ) gracilis Milne Edwards, 1836, of the Aus- 
tralian seas and Acropora ( Gellaria ) coronata Reuss, 1847, a fossil of the Vicentin. 
Range. — Jacksonian-Recent. 
A. Acropora. 
B. Gastropella. 
C. Paehytheca. 
D. Beisselina. 
Fig. 89. — Genera of the family Acroporidae Canu, 1913. 
A. Acropora saillans, new species, X 20. Vicksburgian, 1 mile north of Monroeville, Alabama. 
B. Gastropella ventricosa Canu and Bassler. 1917, X 20. Midvvayan of Arkansas. 
C. Paehytheca stipata, new species, X20, Midwayan, Crenshaw County, Alabama. 
D. Beisselina trulla, new species, X 20. Lower Jacksonian, Jackson, Mississippi. 
The known species of this genus are : 
Acropora (Eschara) coronata Von Hagenow, 1851 (not Reuss). Maestrichtian. 
Acropora (Gellaria) coronata Reuss, 1847. Priabonian. 
Acropora (Entalophora) grateloupi D’Orbignv, 1851. Lutetian. 
Acropora (Porina) contorta Canu, 1910. Auversian. 
Acropora (Pustulipora) mamillata D’Archiac, 1846. Auversian. 
Acropora ( Eschara ) gracilis Milne Edwards, 1836. Recent. 
ACROPORA TRITA, new species. 
riate 6, figs. 5, 6. 
Description „ — The zoarium is free, cylindrical, bifurcated. The zooeeia are 
indistinct; their frontal is confused with the zoarial surface and it is formed of a 
tremocyst with small scattered pores. It has no salient peristomes. The peristomice 
is oblicpie. elliptical, transverse. 
Measurements. — Peristomice \^l )e mm ’ 
[Ipe—OAo mm. 
