FFESTINIOG GROUP. 9 
oe 
@ 
ad 
> 
Tremadoc. Carnarvon Road. 

Barmouth 
Road. 
Traeth 
bach. 
Porrmapoc Estuary: shewing the relations of the Menevian (c), Ffestiniog (d), Tremadoc (e), and Arenig Groups (f) in the district 
around Portmadoc, N. Wales. By the Rev. A. Sedgwick, LL.D. 1847, and J. W. Salter, 1853—7. The faults are all by J. W. 8. The 
strata, in descending order, are :— 

f. Arenig (or Skiddaw) Group. Dark earthy slates on a base of sandstone (=Stiper Stones, Shropshire). 
e. Tremadoe Group. Dark slates, iron stained, and with felspathic beds—1500 feet thick. 
d. Ffestiniog Group. Thick flaky sandstones, 2000 feet, and a bed of black slate 300 feet. 
c. Menevian Group. Dark slate and sandstone—only the top beds (with Olenus cataractes). 
oe Middle _. { Sandstones, hard, laminated, flinty, 2000 feet thick. 
d. Ffestiniog Group Lingula flag. ; es 
Upper ( Black Slates, often stained with iron, 200 to 1000 fect. 
Case and Ref to McCoy’ 
Column of SHEERS tho) Miho Grnes Names and References; Observations, &e. Numbers and Localities. 
Drawers. | Synopsis: and Figures of Genera. 

AMORPHOZOA. None yet known. 

Graptolites. POLYZOA or HYDROZOA? (Graptolitide). 
Horny sheaths, with a slen- Considered by Prof. McCoy and some other 
der solid axis, and with nume- authors as Sertularian Zoophytes. I there- 
_rous close-set cells opening fore place them here in the order given to 
| into the common sheath. The them in the Synopsis. (See for their affini- 
ties, Mem. Geol. Surv. Vol. 111. p. 328, and 
Carruthers, Geol. Mag. Vol. v. pl. v.) 
_mouths often armed with 
spines. 
Gh Dictyonema (Graptopora) sociale, Salter (Mem. | a, 12, black slates of Tre- 
elie Geol. Surv. Vol. 11. pl. 4, fig. 1). Vari- | madocand Wern, and other 
ously known as Gorgonia, Dictyonema, and | places, Cefn Cyfarnedd &c. 
Graptopora. A net-like fossil, allied to the | on the Carnarvon Road. 
Fenestella and Polypora of the Bala and | (Presented by Mr. Ash, 
Wenlock rocks: but of horny texture and | 1862.) a. 13, oliveshales 
with cells in double row, like Graptolites. | of White-leaved oak, Mal- 
(Salter, Mem. Geol. Surv. Vol. mi. p. 331.) | vern. (Rev. W. Symonds.) 
9 
-_ 




