90 



BRITISH SILURIAN BRACHIOPODA. 



Obs. Prof. M'Coy informs us that " this species is remarkable for having its mesial 

 ridge (fold) divided in two by a mesial sulcus, in vrhich it agrees with Spirifer bifidus, 

 Roemer, but from which it differs in the lateral ribs being less numerous and not branched, 

 as in that species. The mesial hollow (sinus of ventral valve) is somewhat simple, and 

 sometimes has a slender mesial ridge. In finely preserved examples the striae of growth 

 are regular and prominent." I may likewise observe, that Spirifera bijugosa bears some 

 resemblance in shape and size to Spirifer bijugatus. Von Buch ; but this last seems to 

 possess a smaller number of ribs ; and its sinus and fold appear also to differ somewhat in 

 shape from that of the shell under description. Prof. M'Coy figures the dorsal valve only; 

 and, although I have seen several specimens of both valves, no example I have met with 

 was completely perfect. The species is not recorded in ' Siluria/ nor in Morris's 

 ' Catalogue of British Possils.' 



Position and Locality. — Prof. M'Coy states that Sp. bijugosa is very abundant in 

 the shales of Doonquin, Dingle, County Kerry, and very common in the slates of 

 Ferriter's Cove, Dingle. According to the Geological Surveyors, the rocks at Dunquin,^ to 

 a little north of Clogher Head, are equivalents of the Ludlow beds. The strata at Ferriter's 

 Cove, joining it to the north, and on the coast between Dunquin and Clogher Head, are 

 coloured as ' Wenlock.' TheWenlock rocks of this district (Dingle) are described on the 

 label of the fossil cases of the Museum of the Geological Survey in Dublin as " a slaty 

 and very fossiliferous series, with much interstratified trap." Sp. bijugosa occurs on the 

 north shore of Ferriter's Cove in Wenlock rocks, with (according to Mr. Salter) " Athyris 

 tumida, Atrypa reticularis, Chonetes lata, Leptcena transversalis, Orthis calligramma, 

 0. elegantula, Rhynchonella borealis, Bh. rotunda, Strophomena compressa, St. euglypha, 

 St. funiculata, St. imbrex, and St. pecten" as well as with many species of Corals, 

 Conchifera, Gasteropoda, Annelida, and Crustacea, peculiar to beds of the Wenlock age. 

 It is further stated by Mr. Salter, who surveyed the ground (p. 13 of the same 

 ' Explanation'), that Sp. bijugosa occurs also in the Croaghmarhin or Aymestry beds in 

 the same district, which contain abundance of Pentamerus Kniglitii, P. galeatus, Ehyn- 

 chonella Wilsoni, and other fossils, such as are found in the Aymestry rocks of Siluria 



^ This locality is spelt Dunquin on the one-inch map of the Ordnance Survey, also in the ' Explanation 

 of Sheets 160, 161, 171, and 172, of the Geological Survey of Ireland, 1863,' where will be found 

 an excellent description of the beds and fossils by Messrs. G. V. Dunoyer and J. W. Salter. Mr. Baily 

 informs me that Dunquin is a parish of some extent on the coast, joining Dunurlin, which includes Ferriter's 

 Cove ; there is also a village of Dunquin, south of Clogher Head. He tells me that Wenlock rocks, with 

 interstratified igneous rocks, much faulted, occur on the coast north and south of Ferriter's Cove, between 

 that and Clogher Head, as may be seen on the one-inch map. Sheet 1/1 ; also, that Ludlow rocks 

 occur in the district ; but that after having carefully searched the registers of fossils of the Irish 

 Geological Survey, he could not find Sp. bijugosa in any locahty of the Ludlow Rocks, but always in 

 those coloured as Wenlock, and abundant at Ferriter's Cove, that is, in the parish of Dunurlin, and 

 also in what are considered to be the same rocks on the coast south of Clogher Head, in the parish of 

 Dunquin. 



