Yol. 69.] JURASSIC AMMONITES FROM JEBEL ZAGHUAN. 569 



probably like 0. Mspidum Opp. as figured by Favre, or even like 

 0. canaliculatum Von Buch. It is only towards the end of the last 

 whorl that the crescents of the outer area appear ; previously to 

 that the sides are smooth, and show only the spiral groove. 



Genus Taramelliceras de Camp. 

 Taramelliceras cf. anar (Oppel). 



1863. A. Oppel, 'Ueber Jur. Amm.' Pal. Mitt. Mus. d. K. Bayerisch. Staates, 



p. 207 & pi. lv, %. 1. 

 1871. M. Neumayr, ' J urastudien : 4 — Die Vertretung dei" Oxfordgruppe im 



ostlichen Theile der M edi terra n en Provinz ' Jahrb. K.K. Geol. Reichs- 



anst. vol. xxi, p. 366 & pi. xviii, fig. 5. 



The first half of the last whorl of my specimen is quite smooth 

 (perhaps worn), and it is only with some hesitation that I refer it 

 to Oppel's form. The latter part of the last whorl, however, is 

 much like fig. 1 d of Oppel's pi. lv, and the specimen also agrees in 

 section and umbilicus so well with the figures, that, if not identical 

 with the type, it must at least represent a very closely-allied 

 form. 



Neumayr's specimen differs from mine in section, as well as in 

 its larger umbilicus, and it seems doubtful whether it is really 

 identical with Oppel's type. 



Genus Lissoceras(?) Bayle. 

 ' Lissoceras ' erato (d'Orb.). 



1847. A. d'Orbigny, ' Pal. Franc. : Terr. Jurass.— Cephal.' p. 531 & pi. cci, 



figs. 3-4. 

 1875. E. Favre, 'Descr. des Foss. du Terrain Jurass. de la Montagne des 



Voirons ' M6m. Soc. Pal. Suisse, vol. ii, p. 28 & pi. i, fig. 15 a. 



A small ammonite, somewhat fragmentary, but showing the 

 inner whorls well, clearly belongs to this form. Its smoothness 

 and flatness, combined with a rounded venter and fairly open 

 umbilicus, make it easily recognizable. 



Another nearly complete and larger specimen has the umbilicus 

 somewhat narrower, probably measuring only 27 per cent, of the 

 diameter, as compared with the 30 per cent, in D'Orbigny's type. 

 It also seems that the periphery is slightly more acute in my 

 specimen than in the type ; but, as the ammonite is worn, I include 

 it with the other specimen in D'Orbigny's well-known ' species,' 

 which is so common a fossil of the Argovian. 



In accordance with present custom, I leave his form in the 

 genus ' Lissoceras' Bayle ( = Haploceras Zittel) ; but there can be 

 no doubt that the Argovian forms have no generic connexion with 

 the true Bajocian Lissocerates. It seems that several lineages 

 within the Oppelidse developed these smooth, rounded forms, and 

 increased knowledge and more material will doubtless enable us to 

 assign to those later groups, which, wrongly, have been put in the 

 genus Lissoceras, their proper places within the family Oppelidaa, 



