18 
THEONOID^. 
Fig. 13, p. 17. Part of a horizontal section across another 
specimen ; X 20 dia. Maastrichter Kalk : Maastricht. Van 
Breda Coll. D. 3512. 
Fig. 14. — Actinopora diadema\ x 10. Fig. 15. — Actinopora d\adema\ x 8. 
D. 3451. D. 3451. 
Fig. 14. The upper surface of a young zoarium, 2 mm. in dia., 
attached to a compound specimen formed of two fused zoaria ; 
X 10 dia. Maastrichter Kalk: Maastricht. Yan Breda Coll. 
D. 3451. 
Fig. 15. The upper surface of a more advanced hut still 
young colony ; X 8 dia. The colony is 2-5 by 3‘5 mm. in dia. It 
is attached to the same zoarium as specimen shown in Fig. 14. 
Maastrichter Kalk : Maastricht. Yan Breda Coll. D. 3451. 
Affinities. 
This species is common at Maastricht, and is characterized by its 
triangular teeth. Yon Hagenow appears to have included under 
this name two forms, of which one belongs to this species, and 
the other (von Hagenow, pi. iv. fig. 4, not fig. 3 as stated, owing 
to a misprint) is a Lichenopora costata. The openings on the 
floors of the interradii of the former specimen {ibid. pi. iv. fig. 2) 
are due to the breaking away of the epizoarial layer present in 
perfect specimens. 
Hamm’s genus Patenaria may be based on this species {vide 
p. 25). 
The development of this species is illustrated by two figures of 
young zoaria, both of which are attached to a full-grown compound 
specimen consisting of a disc, composed of two colonies. The 
smaller of the young colonies is 2 mm. in diameter. The apertures 
at this stage are uniformly distributed over the surface, and there 
is no indication of any fasciculi. The larger of the younger zoaria 
