RHYNCHONELLA. 



75 



Plate IX, figs. 27 and 28. Two examples from the Tipper Green Sa?id of Farringdon, 



in the collection of Mr. Sharpe ; this shell is one of 

 the rarest in the locality, 

 figs. 29 and 30. Two specimens from the Lower Green Sand of the Isle of 



Wight, from the collection of Mr. Morris. 

 fig. 81. A pentagonal specimen, with a very thickened edge, Isle of Wight. 



Genus — Rhynchonella, Fischer, 1809. 



Obs. This genus having been described in p. 93 of the " Introduction," and in 

 Part III, p. 65, it will not be necessary to repeat those details in the present Monograph. 



The most active researches among the British Cretaceous Rhynchonella have not 

 brought to light a single unpublished species, and so numerous are the varieties and 

 passages from one form into another, that it is often almost impossible to draw up a 

 diagnosis embodying the character of every variety. We have admitted the following 

 fourteen species, as well as some few named varieties : — 



fl. Rynchonella plicatilis, Sow. 



var. octoplicata, Sow. 



- var. Woodwardii, Dav. 



- LIMBATA, Schloth. 



- compressa, Lam. 



LATISSIMA (LATA), Sow. 



GlBBSIANA, Sow. 



PARVIROSTRIS, Sow. 



DEPRESSA, Sow. 



var. A. 

 var. B. 



t.8. NUCIFORMIS, SOW. 



12 ? 



5. 

 6. 



(7. 



9. Rhynchonella sulcata, Parkinson. 



10. — Mantelliana, Sow. 



11. — Cuviem, D'Orb. 



12. — Martini, Mantell. 



13. — Grasiana, D'Orb. 



14. — line ata, Phillips. 



Some Palaeontologists may, perhaps, consider R. limbata, Schl. (== sub-plicata, of 

 Mantell) as only a variety of R. plicatilis, and it may be still a question whether R. 

 Grasiana is more than the adult condition of R. Martini, Mantell. Mr. S. P. Woodward 

 considers R. octoplicata as specifically distinct from R. plicatilis, and Mr. Sharpe admits 

 R. triangularis, Wahl., among our British species. 



34. Rhynchonella plicatilis, Sow., Sp. Plate X, figs. 37 — 42. 



var. octoplicata, Sow. Plate X, fig. 1 — 17. 

 var. Woodwardii, Dav. Plate X, figs. 43 — 46. 



Terebratula plicatilis, Sowerby. Min. Con., vol. ii, tab. 118, fig. 1, 1816, 

 — octoplicata, Sowerby. lb., fig. 2, 1816. 



