Rev. J. F. Blake — On Ammonites. 163 



to the Quart. Journ. Geol. Soc, Feb. 1904. As these conclusions 

 do not appear to be well known, it may be as well to quote them. 

 Nikitin^ says: "Having found in the British Museum the original 

 of Am. biplex, Sow. (tab. 293, fig. 1), I assured myself that that 

 original presented absolutely the Oxfordian form of Perisphinctes 

 of the group of P. pUcatilis, by the character of its numerous 

 straight rounded ribs, by the mode of enrolment, by the constriction 

 of its perfectly visible whorls, and lastly by the matrix ; it 

 showed no resemblance to the Kimmeridgian and Portlandian 

 forms described in France and England under this name . . . 

 Mr. Loriol had not seen the original of Sowerby . . . but 

 having received from England, under the name of A. biplex, Sow., 

 the Portlandian forms, he was justified in giving this name to the 

 same form from Boulogne. On studying the English Kimmeridgian 

 forms placed in the museums of England under the name of 

 A. biplex I found amongst them the typical form of A. PaJlasi, D'Orb." 



Professor Pavlov deals only with the latter species,^ saying, 

 " Perispli. biplex (Pallasianus) is the commonest form of our virgatus- 

 beds, and its synonymy with the English form has for a long time 

 been recognized " ; and again, " Amongst these fossils [enumerated 

 by Phillips] Am. biplex can, according to all appearances, be placed 

 in synonymy with our Perisph. Pallasi." 



These, then, by the concurrence of two well-qualified observers, 

 may be considered settled points in any revision of our Upper 

 Jurassic Ammonites. But it may well be asked how came so many 

 English geologists thus to misname their own species. It would 

 appear to have been in this way. Geologists of old cared less for 

 the names than for the specimens themselves, and when Fitton ^ 

 submitted his fossils to J. de C Sowerby, the son of J. Sowerby and 

 successor in the Min. Con., and was told that the characteristic 

 Ammonite of the Kimmeridge Clay and Lower Portland was called 

 Am. biplex, it became so to him, and to all who followed him, without 

 inquiring into the name. This name being thus occupied, Phillips 

 used for the common Malton fossil the other name,* as the only 

 one unoccupied, referring to a somewhat similar and not well- 

 distinguished Ammonite. It thus became ' Am. pUcatilis,' and was 

 so understood even by Nikitin himself. 



Leaving, however, names alone, which, though useful, may some- 

 times mislead us, it is common knowledge that one species figured 

 by Loriol, Damon, Phillips (Geol. Oxf., pi. xv), and Woodward, is 

 characteristic of the Upper Kimmeridge, while another species, figured 

 hy Sowerby in pi. 293, figs. 1, 2, is the characteristic fossil of the 

 Coralline Oolite; but as to the species figured by him in pi. 166, 

 it has never to my knowledge been found in situ, so that its exact 

 horizon is not known. This being the state of affairs, we will see 

 how much further we are carried by the observations of Miss Healy. 



* " Excursious dans les Musees, etc., de I'Europe occidentale " : Bull. Soc. Beige 

 •Geol., torn. iii. 



* " Etudes sur les couches Jurassiques et Cretacees de la Bussie." 

 ^ " Strata between the Chalk and the Oxford Oolite." 



*" Geology of Yorkshire," p. 102. 



