196 BRITISH SILURIAN BRACHIOPODA. 
(the name he adopts for the shell under description), that it is very variable in shape, and 
that to some of its modifications or varieties Pander had applied the distinctive specific 
designations of Porambonites intercedens, P. alta, P. elevata, P. pentagona, P. lata, 
P. plana, P. trigona, P. subrecta, P. latissima, P. parva, and P. rotunda. I cannot help 
expressing surprise that so distinguished a paleontologist as Dr. C. H. Pander should not 
have himself perceived that there would be no limit to the number of so-termed species, if 
to every slight modification of shape or size observable in different specimens of every 
species it should be necessary to apply a separate specific denomination. At page 794 
of his ‘Lethaa Rossica’ M. E. d’Eichwald would add to the list of synonyms that of 
P. equirostris, Schlotheim, which last name he proposes to adopt as the designation 
under which the species should be recognised ; but Schlotheim’s species, which was briefly 
described, but not figured, at p. 282 of his ‘ Petref. Gothe’ (1820), is evidently distinct 
from P. intercedens by its shape and characters, and is justly maintained by M. de Verneuil 
and other palzeontologists as a separate species. In 1846 Prof. M‘Coy described under 
the designation of Atrypa filosa an Irish shell, which seems to me referable to 7° cntercedens 
or to one of its varieties ; and on carefully examining the surface of some well-preserved 
specimens kindly lent to me by the Director of the Geological Survey of Ireland, I found 
that it was covered with radiating rows of pits placed along the bottom of fine sunken 
striae, exactly in a similar manner to those which M. de Verneuil has represented in 
pl. ui, fig. 44, of the second volume of the ‘ Geology of Russia.” In 1822 Prof. M‘Coy 
describes also (but does not figure), under the name of Porambonites intercedens, some 
doubtful Scottish specimens which had been obtained at Wrae Quarry, in Peebleshire 
(Pl. XXV, figs. 17—19), and are preserved in the Woodwardian Museum at Cam- 
bridge; but neither Mr. Salter nor myself, who have carefully examined the specimens 
so referred, could feel entirely satisfied as to the correctness of this identification. In 
his description of these last-named specimens Prof. M‘Coy observes that he has adopted 
for the species the first specific name out of the synonyms used by Pander in his descriptions, 
although it is rather with the large depressed varieties, named by him C. pentagona, that 
the specimens have the most analogy. 
As I have already stated, our Irish specimens agree very nearly in shape with the 
Russian ones, but the strize are somewhat more strongly marked in the former. Of the 
interior I have represented two fine internal casts (Pl. XX VI, figs. 1, 2), which, I believe, 
belong to the species of which we have given the perfect exterior, but of this I am not 
perfectly certain. 
Position and Locality. P. intercedens occurs in the Caradoc at Dunabrattin, 
Knockmahon, Tramore, County Waterford, in Ireland; and from these localities a 
fine series of specimens may be seen in the Museums of the Geol. Survey at London 
and Dublin. 
No English examples have as yet turned up ; but the species, according to Prof. M‘Coy, 
occurs also in Scotland. 
