part 4] JURASSIC chro:n^ologt : lias. 323 



deduction when not accompanied by a note to that effect is most 

 misleading, as it makes ribs appear unduly approximate. Such 

 reduction may be misleading in other cases in Reynes's figures. 



I haye not altered what was preyiously written about these 

 anatters, but haye appended references to this page. 



It is greatl}^ to be desired that some one with access to the 

 material in the Marseilles Museum should issue an explanatory 

 text of Keynes's plates, indicating which are figures of original 

 spechnens and their localities, which are copies and their sources. 

 It would be a grand monument to one who must haye possessed an 

 almost unique knowledge of Ammonites, and a fitting accompani- 

 ment to a wonderful series of plates. It would help to repair the 

 loss which science undoubtedly sustained in the prematm-e death 

 -of an author who gaye promise of discriminative ability much in 

 advance of his time. 



[Since this p^,per was read I liave found that Neumayr made 

 much the same suggestion, in his review of the work (Xeues 

 Jahrbuch f. Min. etc., 1880, vol. ii, Referate, p. 394.).] 



EXPLANATION OF PLATES XXVI-XXXI. 



[All figures are of the natural size, unless otherwise stated. All specimens 

 are in the Author's collection, unless otherwise stated.] 



Plate XXVI. 



Figs. la-2h. Leptaleoceras ZEPTCjr, sp. nov., p. 285. 



JFig. 1 a. Side view ; fig. 1 h, apertural view. Holotype from Marlstone, South 

 Petherton (Somerset) [Domerian, -pre-gibhosa] ; ex coll. D. S. 

 Darell. Figs. 2 a & 2 b. Same views of a young shell from 

 Middle Lias, Gretton, Winchcomb (Gloucestershire) ; pres. J. G. 

 Hamling. 



Figs. 3 ri & 3 6. Leptaleoceras aff. leptum, p. 285. 



Fig. 3 a. Side view ; fig. 3 b, apertural view. From Middle Lias, Gretton, 

 Winchcomb [Domerian, pre-gibbosa'] ; pres. J. G. Hamling. 



Figs. 4a-4c, Acaxthoplevroceras ri-rsicosta, nom. nov., p. 286. 



Fig. 4 «. Side view, body-chamber, X 0-5 ; fig. 4 b, Avhorl-section, X 0*66, 

 taken at the break : left side is somewhat crushed ; fig. 4 c, view 

 of dorsum of end of last whorl, showing subsidiary costulffi of 

 penultimate whorl. Natural size. From Middle Lias clays, 

 Leckhampton (Gloucestershire) [Hwiccian-Wessexian] ; pres. late 

 Rev. F. Smithe. 



Plate XXVII. 



Figs, la & lb. Radstockiceras co:MPLicATrM, sp. nov., p. 287. 



Fi"". 1 a. Side view, test and carina only on first half- whorl ; fig. 1 b, peri- 

 pheral view, first half of outer whorl ; both figs. X O'o. Lower 

 Lias, (Radstock) Somerset; Deiran, Radstocl-iceras ?/. See also 

 pp. 294-95, figs. 6, 12, 21. 



2c2 



