ZURCHERIA. 
295 
prolonged smootli stage in the inner whorls points, I imagine, to the " modifying 
action of earlier inheritance."' It is not evidence that the species belong to a 
different branch and are nearer to an earlier stage — the smooth stage — than 
is ^^pugnax." 
" Pertinax^' and the new species also illustrate the decline of the unispiuous 
stage into the costate stage, and the retrogression is still further elaborated in 
Uhaldi, which is both biologically and geologically the latest species. In Uhaldi 
possibly the spines are absent altogether, nothing but a costate stage is shown 
(see page 298). Its greater inclusion and more compressed whorls also indicate 
retrogression very clearly. 
The correct position of this genus has been a matter of perplexity to myself ; 
and other authors have expressed widely different views. Douville described it 
as belonging to " the tribe of the Zissoceratinse.'* Haug,^ dealing with a spinous 
species, placed it near the descendants (neben die anderen Nachkommen) of 
Deroceras. Vacek may be said to have held a similar view when he placed his 
species in the genus Hammatoceras. 
I differ from these opinions ; but I am inclined to think Douville was near the 
truth. This, however, is a matter to be discussed later. My reasons for placing 
Zurcheria in the family Amaltheidse and in the sub-family Sonnininse are its 
relationship to Haplopleibroceras — to be referred to in the article thereon, — the 
relationship of Haplopleuroceras and Sonninia, the similarity of Haplupleuroceras 
and " Pleuroceras," and the fact that Sonninia and Amaltheus are so closely 
homoplastic. 
It may be noticed that the elevated superior lateral saddle which is a 
characteristic of Zurcheria is to be observed in Haplopleuroceras, " Pleuroceras,'" 
and also in Lissoceras and Oppelia. The geological position of the genus 
Zurcheria is from the Opalinum-Murchisonse horizon of Cap San Yigilio to the 
Soioerhyi-zone of Toulon ; but in this country the species are all confined to the 
Goiicavum-zone, so that their geological position corresponds with their biological 
relationship. 
' The pbylosienetic series of " Pleuroceras " JiawsJcerense, spinatim, pseudo-costattim, shows exactly- 
similar development. The late appearance of a crenulate carina in the last species is explainable 
by " modified action of earlier inheritance " far better than by supposing a separate stem for every 
difference in the ontogenetic record. Zurcheria is evidently a morphological equivalent of " Pleuro- 
ceras " in all phases. 
- "Gattung Zurcheria,'" ' Neues Jahrbuch fiir Mineralogie, &c.,' Bd. ii, p. 194, 1886. 
