C(mglomej^ates, and Marls of Devonshire. 
17 
detritus being especially abundant. These calcareous nodules 
generally contain fossils, most of which, as might be expected, are 
the prevalent forms found in the parent limestone beds of the 
district ; thus the sponges Stromatopora polymorpha and S. placenta, 
so characteristic of the Bishopsteignton limestone, are the prevalent 
fossils in the Conglomerate pebbles from the mouth of the Teign to 
Hole Head ; whilst Smithia Hennahn, so common at Barton, 
near Mary Church, as to have obtained the local name of " Barton 
Star," is one of the prevalent fossils in the Conglomerate cliffs 
of the same parish. So well established is this generalization, that 
a fossil collector can as readily name the Conglomerate locality 
whence a nodule containing a characteristic fossil was taken, as he 
can the Limestone quarry in which the same organism w^as met with. 
On the other hand such cosmopolitan forms as Stromatopora ramosa 
and S. concentrica occur eveiy where, both in the parent, and in the 
derivative, beds. 
Fragments of Devonian slate are as abundant as, from the soft and 
fissile character of the material, could be expected. 
Pieces of Sandstone, undoubtedly of Triassic origin, are 
occasionally met with. 
From Hole Head to Langstone Point limestone fragments are 
rare, and the materials seem to have been mainly derived from the 
Carboniferous countrj^ between Haldon and Exeter, and west of 
that line. 
Trap pebbles are numerous everywhere, and seem to be referrible to 
two distinct kinds of rock ; one of which is apparently identical with 
the trap of Pocombe Hill, near Exeter, and other localities north and 
north-west of Haldon. There seems some difficulty in identifying 
the second kind. Not unfrequently they are porphyritic, the large 
felspathic crystals being sometimes of the variety known as 
Murchisonite ; which, according to Mr. R. Phillips, consists of 
Silica 68,6, Alumina 16.6, and Potassa 14.8.- Pebbles of this 
nature are more or less abundant between Petitor and Teignmouth. 
Many of the porphyritic nodules are found, especially at 
Livermead in Torbay, in a state of decomposition, and are, in some 
instances, reduced to a more or less plastic paste. 
Though Greenstone abounds in various places near the 
Conglomerates, extremely few fragments of this rock occur in them ; 
this is the more remarkable since it is well known that some of the 
Greenstones are of pre-Triassic age. Thus, Mr. Godwin-Austen 
has shown that some of them are contemporary with the older 
Devonian slates,! and the volcanic ash on the flanks of the 
Greenstone of Knowle Hill, at Newton Bushel, contains the 
• " Outlines of Mineralogy, «fec.," vol. i, page 289. 
t " Qeol. Trans,," vol. xi^ part ii^ page 470, 
