Smy'J'H — The Carboniferous Coast-Section at Malahide. 17 



Now we must place these beds either below all others in the section, i.e. 

 low in Z, or above all, i.e. in C. 



We have seen that the evidence from structure is in favour of the latter, 

 i.e. down-throw to the south (see p. 10.) The following facts seem to me 

 to settle the matter in favour of this interpretation : — 



1. Two specimens of Caninia cylindrica, Scouler, were found : one near 

 the middle, the other in the lowest exposed beds. 



2. At M I'M, the lowest beds of the group under consideration, was 

 found a fragmentary pedicle valve, about 40 mm. in length, which agrees 

 with Spirifer princeps, McCoy, in its shape, its broad, flat ribs splitting into 

 two unequal parts, and its fine reticulate pattern. This species is characteristic 

 of the Tournaisian knolls (-y - C,) of Belgium and Ireland, e.g. St. Doulagh's, 

 County Dublin. 



3. Producttis cf. concinnus agrees perfectly with a form common at 

 St. Doulagh's. The Producti found elsewhere in the section do not. 



4. Spiriferina odoplicata has rounded cardinal angles and strong lateral 

 ribs, as in Mut. S, Vaii. 



5. Michelinia cf. tenuisepta and CJionetes squamata occur in C of Rush. 



6. Zophophyllum suggests the higher, rather than the lower, level. 



The evidence for regarding the M 13 beds as the highest in the section 

 may be tabulated as follows : — 



(ff) The structure immediately at the fault (see p. 10). 



(6) The direction of throw of neighbouring parallel dislocations (p. 10). 



(c) Agreement with the railway fault in direction and amount of throw 



(p. 11). 



(d) The fauna, just stated. 



The only evidence against this is the similarity in lithology of M 13 to 

 the "Lower Limestone Shales " of the S. of Ireland and S. Wales (see above, 

 p. 11). 



The thickness of the beds exposed IST. of the Carrickhill fault is about 

 780 feet. The stratigraphical throw of the fault therefore must be at least 

 780 feet + the unknown (but probably small) thickness of beds cut out by 

 the N. fault. 



Correlation with Edsh and with the N. W. Province. 

 Owing to considerable difference in the fauna, close correlation with Kush 

 could not be made. The whole of the Malahide exposure seems to be 

 equivalent to part of the Eush Slates, Z^ - Cj (see L. B. Smyth, Proc. R. Dub. 

 Soc, vol. xiv (N.S.), p. 535. 



