MARINE SPONGES. 
7 
As to the question what we should call the Penmaenmawr 
rock, we are met by the ever-recurring difficulty that, accord¬ 
ing to the German petrologists, the geological age is a factor 
in the question, and I do not know that any indication of the 
age of the mass is known. It is certainly newer than the 
Lower Silurian flags and grits through which it has broken 
its way, but no newer rocks are pierced by it, so that we have 
a sufficiently wide range. Assuming, however, as is probably 
the case, that it is at any rate pre-Tertiary, the main mass 
may be fairly called with Rosenbuscli an enstatite diabase, 
for the structure is in great measure that fully crystalline 
one characteristic of the diabases, and the prevailing 
pyroxene is certainly the rhombic one. 
REPORT ON MARINE SPONGES* 
OBTAINED IN THE OBAN DREDGING- EXCURSIONS OF 
THE BIRMINGHAM NATURAL HISTORY AND 
MICROSCOPICAL SOCIETY IN JULY 1881 AND 1883. 
BY II. J. CARTER, ESQ., F.R.S., ETC. 
1°.—Specimens collected by the dredge on board the 
“Curlew” in about 15-30 fths., together with others gathered 
on the shores of the Island of Kerrera, respectively, in 1881. 
The Sponges having been separated from the other debris 
in this collection, and the species of the former from each 
other, they have been tied up in separate pieces of calico, 
numbered as follows :— 
1. —Hymeniaculon carnosa, Bowerbank (Monograph of 
British Spongiadte, vol. iii., pi. 86). 
2. — Halichondria Pattersoni , Bk. (75., pi. 46). 
3. — Hymeniacidon suberea, Bk. (lb., pi. 36). 
4. — Microciona arrnata , Bk. (lb., pi. 23). 
5. — Halichondria panicea, Bk. (lb., pis. 39 and 40). 
6. — Isodictya fucorum, Bk. (Ib., pi. 56.) 
7. — Debris, consisting of Shells, Ascidians, Polyzoa, Fuci, 
&c., &c. 
The specimens collected from the shores of the Island of 
Kerrera are all of one species, viz., Halichondria panicea. 
* Transactions of the Birmingham Natural History and Micros¬ 
copical Society. Communicated by Mr. W. R. Hughes, November 
11th, 1884. 
