FOSSIL AND EECEjVT LAGO^MOEPHA. 459 



of the identity of the Corsican and Sardinian fossil with tlie Pliocene animal from 

 Roiissillon. 



1 venture to siiggest that the inverse conclusion may he drawn from these statements. 

 The character in question has been figured and exhaustively descinhed in the preceding 

 pages. Of Frolagus sanlus, I have represented on PL 36. three stages. Fig. 11 shows 

 p. 1 of a young individual in which the two enamel foldings {b and c) are large and 

 confluent on the outer margin. In tig. 21 (p. 1 from an adult and rather old individual), 

 they are seen to be separated from each other and reduced to the shape of central 

 enamel islets. Fig. IG exhibits an intermediate condition (see p. 456). If these 

 chevrons are not represented in Lortet's figure quoted by Deperet, this is due to an 

 inadvertence of the artist ; for an examination of the figure quoted shows that the 

 artist had seen something of the kind, but omitted to represent it accurately. In the 

 vast number of maxillaries of Prolaf/us sarcitis from Bastia and various Sardmian 

 localities which have passed through my hands, I have never missed the presence in 

 p. 1 of the two enamel folds ; but it is possible that they may disappear in very old 

 individuals. The fact that, of the only two specimens from Roussiilon examined, this 

 cliaracter was absent in one, proves in my ojiinion that the Roussillon species, although 

 geologically older, has exceeded the island species in the transformation of the cheek- 

 teeth, thus representing the last stage of Prolagiis ; /. c. that which approaches closest 

 to the condition shown by p. 1 of Lagopsis and LagonnjH. 



The peculiarity which 1 am about to mention in the anterior lower premolar of the 

 Frolagus from Casino is not recorded l)y Deperet in the lower p. 2 from Roussillon ; but 

 it would be worth while to re-examine this tooth in the specimens from the latter place ; 

 for the two Prolagi from Roussillon and Casino may be identical, if we judge from the 

 association of other identical species in the two localities. The same may be said of the 

 fossils from Roussillon and Montpellier ; but the information concerning the Frolagus 

 from the latter locality at present at our disposal is insufficient for close comparison with 

 other fossil forms. 



Prolagus elsanus, Maj. 



Myolayvs elsanus, Forsyth Major, Atti Soc. Tosc. Sc. Nat. i. pp. '220. ,2.38 (1875) ; id. in L. Riitimeyer, 

 Ueber Pliocen und Eisperiode auf beiden Seiten der Alpeii, p. 15 (187()) ; id. Atti Soc. Tosc. Sc. Nat. 

 Proc. Verb. p. xc, ] 1 jMaggio 1879. 



A few fragmentary mandibular rami from the Lower Pliocene lignites of Casino, Val 

 d'Elsa (Tuscany), preserved in the Pisa Paloeontological Museum, have been long ago 

 noticed by me, and I have on various occasions stated that, by the conformation of their 

 lower anterior premolar (p. 2), their reference to Hensel's genus Myolagus {Frolagus) is 

 beyond doubt. As at the time no species of Frolagus had been recorded from the 

 Lower Pliocene, I felt justified in assigning a new specific name to the Casino fossil. 



Of some importance, not only as distinctive for the species, is the following character 

 not previously recorded by me, but of which I was perfectly aware at the time, for it is 

 shown in tuo sketches which I made of the lower anterior premolar, right and left, 

 presumably of the same specimen. At the postero-internal margin of tbis p. 2 is a 



64* 



