Smith. I ^Ob [Ot-t. 2. 



the common radicle, Ibergiceras, in several parallel series or subfamilies, 

 including the Medlicottinm, the NoritinK, and the Lecanitince of the 

 Permian and Trias, the Piiiacoceratidiv of the Trias, and the Amolthei- 

 d(K of the Trias, Jura and Cretaceous. 



Dr. K. von Zittel* says that this family jirobahly also gave rise to llie 

 Ceratitidxe of the Permian and Trias. 



Genus Pronorites, Mojsisovics. 



In the adult stage Pronorites is discoidal, has high, narroAv whorl, 

 with nearly parallel sides, is very involute, and has narrow umbilicus. 



The siphoual lobe is three-pointed, the first lateral lobe divided into 

 two or three parts by secondary sinuses. In addition to these there are 

 several auxiliary lateral lobes, three to six, all slightly pointed, while 

 all the saddles are rounded. No constrictions or other surface ornamen- 

 tations are known, except that on the adult body-chamber faint ribs 

 liave been observed. 



The first septum of Pronorites is latisellate, and the broad sinus is soon 

 divided by a siphonal lobe into two lateral sinuses (PI. xxiii, Fig 7). 

 This is the end of the embryonic stage, in which the shell is seen to 

 belong to an ammonoid cephalopod, but the familj' is not yet indicated. 



In the next stage the lateral sinuses are subdivided hy broad, rounded 

 lobes ; the sutures then resemble those of Goiiiatites (Ihergiceras) tetrti- 

 goitus Roemer of the Upper Devonian, and the shell is in the beginning 

 of the larval or nepionic stage (PI. xxiv, Fig. 9ft) ; a little further on the 

 sutures are like those of a Prolec/inites (P. serpentinus Phillips), and 

 the larval stage is approaching its end. 



In the following or neanic stage the siphonal lobe becomes three- 

 pointed, and the shell corresponds to Paraprolecauites Karpinsky.t and 

 its familj^ affinities are beyond doubt (PI. xxiv, Fig. db). 



With the adult or ephebic stage the first lateral lobe becomes divided 

 into two or three parts (PI. xxiv, Fig. 9c-/). With this stage the genus 

 Pronorites stops. But C4emmellaro:j: has described from the Permian of 

 Sicily a further development of this form in the genus Ptirapronorites, 

 in which the double latei-al lobe and some of the simple ones become 

 serrated. 



Another line of develojiment of Pronorites has been described by 

 Gemmellaro (oj). cit.) as SicDifes, in which all the lateral lol)es 

 become double like the first one. The next higher stages are given by 

 Medlirottin Waagen, in which the siphonal saddles become indented and 

 ammonitic. Karpinsky§ shows that Jledlicottia in its development 

 goes through the Ibergiceras, Prolecanites, Pnriiprolecdiiiten, Pronorites. 

 Sicanites and Promcdlicottia stages. 



* Grundzuge der Palxontologie, 1S95, p. 400. 



\ Ammoneen der Artinsk-Stiife, p. 7. 



I Fauna Calc. Famlinn d. Valle d. Jium Sosio, 1S'^7, \i. (JO. 



§ Amiiiimcen der Artiiisk-Stiifi , p. 41. • 



