PERXA. 87 



aviculoides, Sowerby) were afterwards ' referred by that writer to G. sohnoides, 

 Defrance, whilst the Cenomanian forms from Le Mans, also figured as G. solenoides, 

 were named '' G. subaviculoides. 



The examples of G. solenoides from the Senonian of Aachen figured hy Ilolzapfcl ^ 

 differ from our specimens of G. Forhesiana in the greater height of the posterior 

 ear and in its indistinct separation from the rest of the valve, also in having a larger 

 apical angle. 



Ti/pes. — Two of the specimens figured as G. solenoides by Sowerby (figs. 2, 3) 

 are in the British Museum and came from Shanklin. Another specimen figured by 

 Sowerby (fig. 1), from the Upper Greensand of Lyme Regis, is in the Museum of 

 the Geological Society of London (No. 1555), but is not recorded in Mr. Blake's 

 " List of Types." D'Orbigny's type of G. Forhesiana apparently came from the 

 Crackers of Atherfield, but Professor Boule informs me that the specimen cannot 

 now be found in the d'Orbigny Collection. 



Distribution. — Ferna-hed, Atherfield Clay, and Crackers of Atherfield. Fitton's 

 Bed 3G of Blackofang. Ferruginous Sands of Shanklin. Atherfield Beds of Peas- 

 marsh. Hythe Beds of Pulborough. Sandgate Beds of I'arham Park. 



Gault (zones iii to vii, and viii) of Folkestone. Zone of Ilnjilites interraptus of 

 Okeford Fitzpaine (Dorset). Cambridge Greensand (dei'ived). Upper Greensand 

 of Blackdown. 



Genus — Perna, J. G. Bnujuiere, 17S0. 

 ('Encyc. Method., Vers,' vol. i, p. xiii.) 



Peuna Muli-eti, Deshayes, 1842. Text-figure 15. 



1842. Perna MuLLETi, Des/iayes iu A. Leymerie. Mi-m. Soc. gt'ol. de France, ser. 



2, vol. V, p. 8, pi. xi, figs. 

 1-3. 

 184.5. — — E. Forbes. Quart. Jouru. Geol. Soc, vol. i, p. 246, pi. i, 



figs. 1 — 4. 

 1846. — Uvi.i.Eru. A. d'Orbigny. Pal. Fran?. Terr. Crut., vol. iii, p. 4%, pis. 



cccc, cccci, figs. 1 — 3. 

 1848. — MuLLETi, C. L. Korli. Paloeontograpliica, vol. i, p. 171, pi. xxiv, 



fit's. 14 — 17. 



' ' Prodr. de Pal.,' vol. ii, 1850, p. 250. 



2 Ibid, vol. iii (1852), p. 72 (index) ; d'Orbigny. 'Pal. Fran?. Terr. CrJt.,' vol. iii (1846), p. 489, 

 pi. cccxcvii, figs. 3, 4, 5. Prof. Boule informs me that these ai-e from lie Mans, an.l aiv n.)« in the 

 d'Orbigny collection. 



' • Mollusk. Aachen. Kreide' (1889), p. 223, pi. xxiv, figs. 11, 12. 



