TRANSLATIONS AND NOTICES 



GEOLOGICAL MEMOIRS. 



1. PnTLLOCERAS in the Jurassic Series. By Dr. M. Netjmatr. 



[Imperial Geological Institute, Vienna, June 30, 1871.] 



The abundance of species of this genus is a palteontological cha- 

 racteristic of the Mediterranean Jurassic rocks, their occurrence 

 being comparatively rare in those of the neighbouring middle Eu- 

 ropean region. In any well-known deposit containing these Cepha- 

 lopods, four chief types of PhyJloceras may be distinguished ; the 

 representatives brought together from aU. horizons constitute four 

 great series of forms, besides which a few isolated species occur. 

 The members of each series, nearest in geological age, present 

 a striking mutual affinity, although the differences between them, 

 accumulating in the same direction, produce a considerable dis- 

 crepancy between the oldest and the youngest forms. In the first 

 place, the sutured line is continuously modified in one direction, 

 the division and complication of the sellar leaves gradually in- 

 creasing. Analogous, but less important, modifications take place 

 also in the sculpture of the shell ; but very httle regularity is notice- 

 able in the modifications of the general form, transverse section, &c. 

 The four series of forms distinguished by the author are as fol- 

 lows : — 



1. Series of Pliylloceras lieterophyllum. — Sculpture of shell only 

 simple radial striae or folds ; saddles slender, nearly symmetrical ; 

 termination of the first lateral saddle of the inner side one-leafed. 

 The species of this series are : — 



Phylloceras heterophyllum, Sow. Upper Lias. 



trifoliatum, sp. n., Inferior Dogger. 



Kudernatschi, Hauer. Klaus beds. 



Kunthi, sp. n. Kelloway group. 



plicatura, sp. n. Oxford group. 



isotypum, Ben. Aspidoceras-acanthicum beds. 



saxonicum, sp. n. Ibid. 



serum, 0pp. Titbonian. 



ptychostoma, Ben. Ibid. 



Thetis, B' Orb. Neocomian. 



?velleda3, Mich. Gaidt. 



2. Series of Phylloceras Gapitanei. — Internal cast with simple 

 furrows inclined forward, corresponding to prominences (never to 

 furrows) of the shell ; distinct radial striae, bending forwards ; 

 saddles slender, iinsymmetrical ; first lateral lobe of the inner side 

 with a two-leaved termination. Species : — - 



VOL. XXVII. PART II. B 



