PROM THE ZONE OF AMMONITES RARICOSTATUS. 61 



The breadth of the calice is ^^ths inch, and the height foths inch. 



Locality. Penny Compton. 



In the Collection of R. Tomes, Esq. 



The shape and the peculiar base distinguish this species. 



4. MoNTLiVALTiA KADiATA, Duncan. PI. XV, figs. 1 — 5. 



The corallum is small, circular, discoid, and very flat. The wall is almost horizontal, and 

 has a central depression. The calicular margin presents radiating septo-costal ends, which 

 project. 



The calice is very shallow, circular, and presents four principal septa. 



The septa are unequal. The longest reach into the axial space, and are more exsert 

 than the others. There are thirty-six septa, and a few rudimentary laminse. The quater- 

 nary arrangement is obvious. The septa are stout, straight, and granular. 



The costse are very distinct, and are covered with a pellicular endotheca, which presents 

 transverse ridges between the costse. No dissepiments can be discovered. 



The diameter of the corallum is i^ths inch, the height ~th inch. 



Locality. Penny Compton. 



In the Collection of R. Tomes, Esq. 



This is a very abnormal species, and retains the quadrate septal arrangement which 

 is faintly preserved in many Liassic Corals, but which is so characteristic of many Palaeozoic 

 forms. The pellicular epitheca is very remarkable. 



XVII. — List of Species from the Zone of Ammonites raricostatus. 



Montlivaltia rugosa, Wright, and many varieties. 



— mucronata, Duncan, and many varieties. 



— nummiformis, „ 



— radiata, „ 



XVIIL List of Species from the Zones of the Lower Lias above the Zone ov 



Ammonites angulatus. 



1. Montlivaltia Guettardi, Blainville. 



2. — patula, Duncan. 



3. — rugosa, Wright, sp. 



4. - — mucronata, Duncam 



5. — nummiformis, „ 



