Vol. 69.] JURASSIC AMMONITES FROM JEBEL ZAGHTTAN. 557 



from which point the sides slope very gradually to the periphery 

 as well as to the umhilicus, although the final edge at the latter 

 is quite sharp. 



The periphery, as in Fucini's forms, is ' little spacious ' and 

 narrowly rounded, bearing a. small keel. Fucini does not state 

 whether this is solid or hollow, and his illustrations are certainly 

 far from good ; but he compares his fossils with ammonites de- 

 scribed by Meneghini as A. lythensis Y. & B., a form which belongs 

 to the hollow- carin ate genus PseudoJioceras. The latter author * 

 also omits to describe the character of the carina. 



Now, on the penultimate whorl the form at present considered 

 is distinctly solid-keeled, like the typical Aalenian Liocerates. The 

 section is here also less lanceolate and quite rectangular, with a 

 comparatively broad periphery. 



The ornament consists of strong primary eostoe near the um- 

 bilicus ; and, whereas Fucini's form shows fourteen, my specimen 

 possessed probably eighteen to twenty. These costae bifurcate at 

 the middle of the side, but somewhat irregularly, and the whole of 

 the radial line describes the double curve which is characteristic 

 of the true Liocerates. There are also intermediate costae, and 

 altogether the character of the costation agrees exceedingly well 

 with that of Lioceras gvacile S. Buckm. and, less so, with L. sub- 

 costosum S. Buckm., 2 both these true Liocerates coming from the 

 scissi beds. 



Some Pseudoliocerates show superficial resemblance to this 

 specimen. Quenstedt's Ammonites cf. lythensis (non Y. & B.) 

 pi. liv, fig. 54 (' Amm. d. Schwab. Jura' 1885), is too thick 

 near the umbilical edge and too involute ; whereas the style of 

 costation is comparable with that of the form now described only 

 near the end of the last whorl. 



Ammonites elegans (non Sow.), figured by P. Reynes, 3 also has a 

 different section, and the costse do not seem to be biarcuate ; 

 PseudoUoceras beyrichi Schloenb., 4 on the other hand, has an 

 approximately similar radial line. 



A new generic name might be introduced for these ' Prolio- 

 cerates ' of Domerian age ; but, as the sutures of neither Fucini's 

 grecoi nor of my specimen are known, and as they are altogether 

 poorly preserved, I will neither venture to propose one myself, nor 

 to speculate on the connexion of the group with the other Middle 

 Liassic Hildoceratidee. 



1 Gr. Meneghini, ' Fossiles du Meclolo ' [in Stoppani's ' Pal. Lombarde ' 

 ser. 4, App.] p. 3 3 (pars). 



2 ' Inf. Ool. Ammonites : Snppl.' pt. 10, Monogr. Pal. Soc. vol. Hi (1898) 

 pi. vi, figs. 11-13 & 5-7. 



3 ' Monographic des Ammonites du Lias Super.' pi. v: for example, fig. 10. 



4 U. Schlcenbaeh ' Beitr. z. Palaont. d. Jura- & Kreide-Format. in N.W. 

 "Deutschland : I — Jurass. Amm.' Palaeontograpbica, vol. xiii (1865) pp. 170-71 

 & pi. xxvii ; also S. S. Buckman, ' Inf. Ool. Amm.' pt. 3, Monogr. Pal. Soc. 

 vol. xlii (1888) p. 87 & pi. xx, figs. 7-10. 



