6 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



aperture has an undulating outline, and there is a constriction in the cast of the 

 body-chamber just below the aperture (PL I, fig. 3 d). Septa exceedingly 

 numerous, undulating, varying very little in their distance apart, this regularity 

 being a marked feature in the species. Siphuncle small, cylindrical, central. 

 Test quite smooth. 



Size. — The largest specimen, a cast, entirely septate, and imperfect at both 

 extremities, has a length of 240 mm., the greatest diameter being 38 mm., the 

 least 13 mm. ; thus the apical end wants but little to make it complete. It may 

 be added that about 25 mm. of the larger end of the specimen are omitted in the 

 figure to save space. 



Affinities. — In general shape, multitude of septa, and position of siphuncle the 

 present species resembles Ortlioceras inopinatum, de Kon., 1 but the latter tapers 

 more rapidly, and has still more numerous septa. 0. Nerviense, de Kon., 2 has also 

 closer septa than 0. Sancti-Doulaghi. 



Remarks. — The salient character in this species is the great regularity and 

 equality of the septation. The slight ellipticity of the adult portion of the shell is 

 a feature of common occurrence in straight-shelled Orthoceratites, the apical part 

 being usually either circular or much less elliptic than the older part. The 

 specimen figured has its surface roughened by chemical erosion, but the sutures 

 though obscured have not been obliterated, nor are the septa as seen in a section 

 injured. The siphuncle has, however, been destroyed by the formation of small 

 crystals of calcite, which entirely fill the chambers. 



Locality. — St. Doulagh's, 3 county of Dublin. 



Orthoceras acre, A. H. Foord. Plate II, figs. 2 a — d. 



1896. Orthoceras acre, A. H. Foord. Ueber die Orthocereu des Kohlenkalks 



(Carboniferous Limestone) von Irland. . . . In- 

 augural-Dissertation zur Erlangung der Doktorwiirde 

 . . . der Kgl. bayer. Ludwig-Maximilians-Uni- 

 versitiit zu Munehen, p. 12. 



1 Faune Calc. Carb. Belgique ('Ann. Mus. Boy. d'Hist. Nat. Belgique, ser. Paleont.,' vol. v), 

 pt. 2, p. 63, pi. xl, fig. 1 ; pi. xlii, fig. 2. 



2 Loc. cit., p. 57, pi. xl, figs. 2, 3. 



3 A village about six miles from Dublin, where extensive quarries in tbe Carboniferous Lime- 

 stone have long been worked. Tbe parish church of St. Doulagh's, giving its name to tbe village, is 

 of considerable antiquity, dating probably from the latter end of the thirteenth century ; it is reputed 

 to be the smallest church in Ireland. There is a description and picture of it in W. F. "Wakeman's 

 ' Archaeologia Hibernica.' 



