GEOL.-VOL. I.] SMITH— LVTOCERAS AND PHYLLOCERAS. 141 



has only one internal lateral lobe on each side of the anti- 

 siphonal, and the metanepionic stage of L. alamedense 

 shows two (PI. XVIII, figs. 2 and 3, 4 and 5). This 

 character suggests some early ammonite derived from the 

 Prolecanitidse, differing from the goniatite stock in being 

 prosiphonate.^ Such a form is seen in Nannites, named by 

 Mojsisovics ^ to include some smooth, rounded species with 

 simple goniatitic septa, from the Upper Trias, Goniatites 

 spui'ius Muenster being the type. These forms while not 

 ammonitic in sutures or ornamentation of the shell are pro- 

 siphonate. The septa consist of a divided ventral lobe, 

 two external lateral lobes on each side, an internal undi- 

 vided antisiphonal lobe, and two on each side. 



The ontogeny of Nannites is unknown, but it probably 

 comes from some member of the Prolecanitida? ; until 

 recently it was not known below the Upper Trias, but 

 Dr. Carl Diener ^ has discovered it in the Otoceras fauna 

 of the Lower Trias of the Himalayas ; thus Nannites must 

 be a survivor of the Permian ammonite fauna, with which, 

 indeed, it agrees in its chief characters rather than with 

 Triassic faunas. N. hindostaniis Diener {op. cit. PI. VII, 

 figs. 3, II, 12) is broad, with low whorl, open umbiHcus, 

 simple goniatitic lobes and saddles, and shell marked by 

 contractions forming transverse ridges and furrows ; between 

 these contractions the shell is covered with fine strias of 

 growth. The shell lamina? are cut off by the contractions, 

 and sink under the laminae in front, causing what Diener 

 calls "direct imbrication." 



Nannites v^2iS classed by Mojsisovics with the Ptychitidae, 

 but the genus was raised by Diener to a subfamily Nanni- 

 tinae; no connection with the Lytoceratid^ has ever been 

 suggested, but the results of this investigation make it quite 

 probable. L. almnedense at the second septum enters a 

 stage resembling Nannites (PI. XVI, figs. 3 and 4), and 



1 In a recent paper, M6m. Soc. G60I. France. Mgm. XVIII, 1898, "Etudes sur les 

 Goniatites," Professor E- Haug derives the Lytoceratidse from Gephyroccras. 

 - Abhand. K. K. Geol. Reichsanstalt, Wien, Bd. X, 1882, p. 210. 

 * Mem. Geol. Survey, India, Pal. Indica, Ser. XV, Vol. II, Part I, p. 66. 



