Type of Carboniferous Foraniinifcra. 289 



as referrible to a true canal-system, there are appearances that 

 continually suggest the possibility of its existence. 



Incomplete as the above details may appear, they are suf- 

 ficient to show that the new organism has many affinities to 

 the Nummulitic type, though less complex in general structure. 

 Its primary and most striking difference consists in its being 

 formed of a coiled non-septate tube instead of a spiral line of 

 chambers, although the tube shows the same tendency as the 

 Nummuline chambers to bifurcate laterally. 



The difficulty of determining the structure and organization 

 of so minute a fossil is always great ; but in the present case 

 it is much increased by the infiltration with a subcrystalline 

 substance of the same chemical composition as the shell itself. 

 It may be recollected that the true structure of the Nummulite 

 itself, comparatively a large organism, was only made out by 

 the study of non-infiltrated specimens from the sandy Tertiary 

 beds of Hampshire. It is, I fear, too much to hope that a 

 fossil of Carboniferous age may be found in like condition. 



I propose the name AiiCH^EDiSCUS for the genus represented 

 by the fossil I have described ; and in suggesting a specific term 

 I am glad of the opportunity of associating with so interesting a 

 type the name of my friend Dr. Felix Karrer, of Vienna, whose 

 researches have added much to the knowledge of Tertiary 

 Foraminifera. 



The distribution of ArchcecUscus is, so far as we know, con- 

 fined to the Lower Carboniferous Limestone. The first speci- 

 mens which came under my notice were in the collection of 

 Mr. John Young, of Glasgow, who, with characteristic liberality, 

 allowed me to use them in whatever way seemed desirable to 

 elucidate their nature; these were from the Carboniferous- 

 Limestone shale (main limestone) of Brockley, near Lesmaha- 

 gow, in central Lanarkshire. To Dr. Harvey B. Holl I am 

 similarly indebted for the use of his specimens from Great 

 Ormes Head in Caernarvonshire. Mr. David Robertson's 

 collection has also examples from Brgckley; and Mr. E,. 

 Etheridge, Jim., of the Geological Survey of Scotland, has 

 kindly supplied me with material both from this locality and 

 from Shiel, near East Kilbride, in the same county. 



I have dwelt upon the relationship to Nummulina rather than 

 to its allies Operculina and Amphistegina, either of which the 

 new genus more nearly resembles in degree of complexity of 

 organization, because of the interest which attaches to the 

 geological distribution of the Nummuline type. The view 

 that once prevailed, that the Nummulite made its appearance 

 suddenly at the beginning of the Tertiary epoch and gradually 



