Geological Society of London. 239 
felsites of the Dartmoor district; and to point out some of the 
evidence which exists in the in-siéw elvans for the development of 
the most varied of these forms from a common magma. 
Special opportunities for the study of two of the elvanite dykes in 
the neighbourhood of Tavistock have lately presented themselves. 
The Shillamill elvan exhibits a centre composed of quartzose felspar- 
porphyry graduating laterally through numerous varieties into 
“claystone porphyry’; whilst the Grenofen elvan retains the same 
structure in breadth, but changes in length from a rock containing 
so little felsitic matter that it is essentially a fine-grained porphyritic 
granite, to one with a compact semivitreous ground-mass, in which 
felspars, quartz, mica are porphyritically developed. 
As evidence afforded of the existence of distinctly volcanic rocks, 
mention is made of a deposit of water-borne and water-worn detritus, 
indicating a Dartmoor origin for a large portion of its constituents, 
along with rolled flints and pebbles of Carboniferous, Liassic, and 
Cretaceous limestone, with which were associated typical andesites 
and specimens of voleanic grit such as arise from denudation of 
voleanic cones. This occurs on the limestone at Cattedown near 
Plymouth, and bears testimony to a very ancient denudation. 
2. The “Basals of Hugeniacrinide.” By F. A. Bather, Hsq., 
B.A., F.G.S. 
Although Professors Beyrich and v. Zittel had alluded to certain 
specimens of Hugeniacrinus as proving, by the course of the axial 
canals, that in this genus the basals had passed up into the radials, 
yet the two chief authorities who subsequently discussed the subject 
practically ignored this argument. M. de Loriol contented himself 
with denying any trace of basals, while Dr. P. H. Carpenter main- 
tained that the top stem-joint represented a fused basal ring. In a 
previous paper the author had argued in favour of Prof. v. Zittel’s 
view without convincing Dr. Carpenter of its correctness. Such 
scepticism was, no doubt, warranted by the lack of detailed descrip- 
tion and of figures. ‘The object of the present note was to set the 
matter at rest by describing and figuring certain dorsal cups of Hug. 
caryophyllatus kindly lent to the author by Prof. von Zittel. 
Owing to the mode of fossilization the canal system is plainly 
seen. ‘The axial canal passes up into the radial circlet and gradually 
widens; at a short distance below the floor of the calycal cavity it 
gives off five interradial branches; these soon bifurcate, and the 
adjacent radial branches converge. Before they meet, each radial 
branch gives off a very short branch; this connects the radial 
branch with the ring-canal that contained the interradial and intra-- 
radial commissures. 
The evidence of all other Crinoids that have these canals shows 
that the basals always contain the interradial branches. And in 
Bugeniacrinus, since the interradial branches have their origin in the 
middle of the radials, the basals must have passed up in between 
the radials, 
8. “On some Polyzoa from the Inferior Oolite of Shipton Gorge, 
Dorset.” By H. A. Walford, Esq , F.G.S. 
