258 ANCYLOCKHAS. KAfTI.INA. 



cerax. which seems to be completed in the Parkinsonia. In 

 respect to the genetic relationship with the Parkinsonia, the 

 inner whorls of the Runcinata are above :ill decisive, whicli. as 

 is well known, possess the characters of the Parkinsonia. 



I place here provisionally, the small group of Macrocepha/fi. 

 the affinities of which await more thorough investigation ; on the 

 <nic hand their reference to Oosmoceras is indicated by the re- 

 markable resemblance of the last whorls of Oosm. Gallilaeii, 

 while on the other the inner whorls of the Macrocephala present 

 no trace of the siphonal furrow, and also in form and ribbing much 

 analogy exists with inflated species of Siephanoceras with nar- 

 row umbilicus. The Macrocephala are strangers in the European 

 Jurassic fauna, which, in our part of the world appears only for 

 a short time ; when we have learned to know more accurately 

 their ancestral limits, only then will a distinction be possible, 

 and probably it will be necessary to establish a distinct genus for 

 their reception. Preliminarily I will regard them as Cosmoceras. 



Forty-two specie-. 



COSMOCERAS GALLOVIENSE. d'Orb. T. 111. tigs. r(iu. (5H1. Ju- 

 rassic. 



Genus ANCYLOCERAS, d'Orb. 



hi the middle .Jurassic a number of evolnte forms appear, 

 which M> fully agree in sculpture and lobular structure with 

 their cotemporary Cosmowra*. that we must, according to the 

 precedent of (Jnenstedt. regard them as forms of that genus 

 which have become evolute. Strictly considered, one could pro- 

 jo>e a new name for them, but to avoid this, it appears to the 

 purpose to adopt the name Ancyloceras, which has become 

 vacant amongst the cretaceous Ammonites since they have been 

 hitherto placed in this genus. The quite smooth initial whorls 

 are verv striking, a character whicli also appears in Gjxm. ver- 

 rucosu in. 



<;-M. is BACULINA, d'Orb. 



In the Suabian Unnilfi clay^. an entirely smooth and straight, 

 form of Ammonite appeal's, which, at the lirst glance, seems 

 eniirmatical and of uncertain reference. I f. however, the 

 initial whorls of the middle Jurassic Ancyloceras are 

 romparrd with llurtiliim fi'-i/aria, we find that aside from the 



