371 



Thecidium Meditereaneum (pi. Ixxiii. f. 30, 31, 32.) Risso. 



Testse valva dorsali gibbosa, postice rostrata, antice subbilobata ; 

 valva ventrali planulata, operculiformi ; intus lameUis ad utrumque 

 latus lobulos duos, alterum semilunatum, magnum, alterum parvum 

 internum eiformante. 



Shell mth the dorsal valve gibbous, produced behind, and some- 

 what bilobate in front ; ventral valve flattened, operculiform ; 

 internal appendage lamellar, forming two lobes on each side, one of 

 wliich is large and semilunate, and the other very small ; they ad- 

 here throughout to the inside of the ventral valve. 



Found ou Corals in the Mediterranean. 



ORBICULA, CRANIA, HIPPONYX, 



AND 



THECIDIUM. 



LIST OF FIGUEES IN PLATE LXXIII. 



Fig. 1. Orbicula lamellosa, 1. 

 2, 3. — laevis, 2. 

 4, 5. — tenuis, 3. 



6. — Cumingii, 4, 



7. — strigata, 5. 



8. — striata, 6. 



9. Crania personata, 1. 

 10, 11. — ringens, 2. 



12, 13, 14. — rostrata, 4. 

 15,16,17. — Norvegica, 3. 



18, 19, 20. Hipponyx Mitmla, 2. 

 21, 22, 23, — subrufa, 3. 



24, 25. — radiata, 4. 



26, 27. — barbata, 1. 



28, 29. — Ticaonica, 5. 



30, 31, 32. Thecidium Mediterraneum. 



