No. I.] LARVAL STAGES OF SCHLOENBACHIA. 245 



The best example of correlation of ontogenetic stages with 

 phylogeny is the genealogy of Mcdlicottia, worked out by Kar- 

 pinsky, who has shown that the Carboniferous genus Projiorites 

 goes through the following stages : latisellate protoconch, phyl- 

 embryonic ; with the second suture it reaches the Anarcestes 

 stage, nepionic ; about the end of the first revolution the Iber- 

 giceras stage begins, paranepionic ; second revolution shows the 

 Paraprolecanites stage, neanic ; on the third whorl begins the 

 Prono rites stage, adult. Thus with regard to Pronorites the genus 

 Aftarcestes is phylonepionic, Ibergiceras is phyloparanepionic, 

 Paraprolecanites is phyloneanic. In the same work Karpinsky 

 has shown that Medlicottia is a direct descendant of Pronorites 

 and in its development goes through all the stages of the ances- 

 tral genus and adds several more. The first revolution of 

 Medlicottia could not be studied, but on the second revolution 

 was seen the Ibergiceras stage, metanepionic ; on the third 

 whorl the Paraprolecanites stage, paranepionic ; at end of the 

 third whorl the Pronorites stage, beginning of the neanic ; on 

 the fourth whorl the Sicanites stage, end of the neanic ; on the 

 fifth whorl the Proniedlicottia stage, anephebic ; and lastly, at 

 end of the fifth whorl, Medlicottia, adult in characteristics, 

 though not yet in size. 



Genus Schloenbachia Neumayr, Sitsiingsberichte k. Akad. 

 IViss. IVien {M^th. Nat. Kl.), Bd. Ixxi, i. Abth., p. 658, 1875. 



As originally defined by Neumayr, Schloenbachia was to include 

 forms with narrow, compressed whorl, strong curved lateral ribs, 

 a sharp, often notched, keel ; septa comparatively little branched, 

 two lateral, and one distinct auxiliary lobe. The genus was 

 supposed to be descended ixova Anialtheiis , although Neumayr ^ 

 says that we can only assign Schloenbachia with probability to 

 this group, since it appears suddenly in the Cretaceous as an 

 immigrant, without local ancestors; it has later been broken up 

 into a number of genera and subgenera of questionable value, 

 some of which cannot be sharply differentiated from each 

 other.2 



* Loc. cit., pp. 654 and 658. 



2 F. B. Meek, " Report on Invert. Cretac. Foss. Upper Missouri," 1876. Gros- 

 souvre, "Les Ammonites de la craie super, de la France," 1893. 



