62 MISS MAUD HEALEY ON [Feb. I904, 



Plate XI. 



Perisplrinctes variocostattis (Buckland). 



This isBuckland's 'type '-specimen, and is preserved in the Buckland Collection, 



at the University Museum. Oxford. 



Plate XII. 



Olcostephawus Pallasianus (d'Orb.), var. nov. 

 Fig. 1. Side view. 

 2. Front view. 

 This specimen is preserved in the Buckland Collection, at the University 

 Museum, Oxford. It is figured as an example of the ammonite which has 

 so long been known as Ammonites biplex. 



Discussion. 



The Rev. J. F. Blake congratulated the Authoress on having 

 come independently, by the study of the type-specimens, to the 

 same conclusions as those foreigners who had studied our Upper 

 Jurassic ammonites. Nikitin and Pavlow had pointed out, after 

 their visit to England in 1888 for the International Geological 

 Congress, that the shell that we had been in the habit of calling 

 Ammonites plicatilis was what they had understood by Am. biplex, 

 and that what we called Am. biplex was what they knew as 

 Am. Pallasianus. M. P. de Loriol also had figured the latter species 

 under the name of Am. biplex. 



The speaker thought that he was in a position to show that the 

 trouble had arisen from Sowerby himself, who, to illustrate his 

 description of Am. plicatilis, had figured the one specimen intended 

 to illustrate his description of Am. biplex : while, to illustrate his 

 description of Am. biplex, he had figured the two specimens intended 

 to illustrate his description of Am. plicatilis. This (said the 

 speaker) was shown not only by a comparison of details, but by 

 the mere fact that Am. plicatilis was spoken of in the plural, and 

 as occurring abundantly and in company with Am. excavatus in 

 places where the easily-recognizable specimens figured as Am. biplex 

 do occur in such company ; while Am. biplex was spoken of as one 

 specimen occurring in Drift, which could not therefore be repre- 

 sented by two examples, though it might well be by the figure of 

 Am. plicatilis, which cannot be recognized as an Upper Jurassic 

 fossil, but whose home might perhaps be now determined, since the 

 Authoress had rediscovered the specimen. The use of the term 

 1 biplex ' for the very distinct Upper-Kimeridge form appears to 

 have been introduced by Fitton, who has been followed by others 

 until corrected by the Russians. 



A curious question arises out of the mistake thus indicated. If 

 an author describes under the same name one specimen in the text 

 and illustrates another specimen in the plates, which is the type ? 

 In the view of the speaker, if they be of different species, the name 



