578 MB. L. P. SPATH ON [DeC. I9I3, 



but represents one of those intermediate forms which seem to be 

 the commonest, and to which, for instance, besides Quensfcedt's 

 figs. 21 & 29, the figures of P. de Loriol, 1 those of A. de Eiaz, 2 

 and also some of Dr. Salfeld's P. toucasi (as, for example, his fig. 3 

 of pi. x) belong. Fig. 27 of Q,uenstedt's pi. xci 3 represents neither 

 an old toucasicmum nor an old transversarium, but a densicosfate 

 fragment of an undetermined variety. With the scanty material 

 at my disposal I refrain from naming these varieties. 



Peltoceras PERVixauiERi, nom. nov. = P. eotjqttei Perv. non Kil. 



1907. L. Pervinquiere, ' Etudes de Paleontologie Tunisienne : I — Cephalo- 



podes des Terrains Secondares ' p. 28 & pi. i, fig. 9. 

 non 1877. G. G. Gemmellaro, ' Faune Giur. & Liass. della Sicilia ' p. 166 & pi. xx, 



fig. 16. 

 non 1889. W.Kilian, 'Mission d'Andalousie : II — Etudes paleontologiques sur 



les Terrains Secondares & Tertiaires de 1' Andalousie ' Mem. Ac. 



Sci. Paris, vol. xxx, p. 631 & pi. xxvi, fig. 2. 



Dr. Kilian's figure shows, at a diameter of 90 mm., an umbilicus 

 measuring 43 per cent, and height of the last whorl 38 per cent. 

 It is only the last three-quarters of the final whorl that are radially 

 recticostate. Before then, the ribs are close, slightly rursicostate, 

 and, finally, seem to be of the usual toucasicmum type. Gemmellaro's 

 form, at a diameter of 150 mm., has an umbilicus measuring 43 

 per cent, also, and the height of the last whorl equals 35 per cent. 

 The inner whorls are badly preserved, but apparently similar to 

 those of Dr. Kilian's ammonite. 



Now, the specimen which Pervinquiere identifies with Dr. Kilian's 

 form has an umbilicus of only 38 per cent., not 43 per cent. ; 

 but, what is more important, the exceedingly coarse and distant 

 costation is essentially radial and straight already at a very 

 small diameter. It probably forms the final development in that 

 direction, and certainly has a good claim to be separated from 

 P.fouquei Kil. 



The ammonite figured by Dr. Salfeld as a large specimen of 

 P. toucasianum from Palermo 4 closely resembles Gemmellaro's form 

 (fig. 16 only), but its dimensions are, at a diameter of 115 mm. : — - 



Umbilicus 38 per cent, of the diameter. 



Height of the last whorl 36 per cent, of the diameter. 



Similarly, a cast in my collection, taken from a specimen from 

 Mcenthal (Switzerland), shows at a diameter of 120 mm. : — 



Umbilicus 39 per cent, of the diameter. 



Height of the last whorl 37 per emit, of the diameter. 



It is equally recticostate on the last whorl. These two forms 

 would, then, represent an involute variety of P. fouquei Kil. ; but 

 the study of the inner whorls of the ammonites belonging to this 



1 Op. git. Mem. Soc. Pal. Suisse, vol. xxx (1903) pi. xv, figs. 5 & 6. 



2 'Description des Ammonites des Couches & Peltoceras transversarium de 

 Trept (Isere) ' 1898, pi. xix, figs. 1-4. 



3 ' Ammoniten d. Schwabischen Jura' 1888. 



4 Op. cit. N. Jahrb. vol. i (1906) pi. xii, fig. 11. 



