32 ORDOVICIAN AND SILURIAN BELLEROPHONTACEA. 



American species B. emmonsi, Ulr. and Scof.,^ and B. haUi, Ulr. and Scof./ may 

 also be compared. The fine ornament in the interspaces is rarely preserved in 

 our specimens, and Eichwald does not show any trace of it in his figures of 

 B. contorta. 



S. Bucania playfairi, sp. nov. Plate VI, fig. 10. 



:!fic Gharacfrys. — Shell subglobose, composed of 3 — 4 low transverse 

 whorls, broader than high ; umbilicus deep, rather more than one-third the 

 diameter of shell, with centre situated at more than one-third the height. Outer 

 whorl gradually increasing in width, swollen and overhanging umbilicus laterally, 

 with convex dorsum, and narrowly rounded umlnlical edge; umbilical slope steep, 

 high. Slit-band narrow, with strong raised edges. Mouth slightly expanded at 

 sides, transverse. Surface of shell marked by equidistant coarse imbricated 

 transverse lamellae, set rather close together, fimbriated at their edges and meeting 

 slit-band at about 60° — 75°, with low rounded spiral ridges in interspaces corre- 

 sponding to fimbriations of lamellae and interrupted by them, set slightly oblique 

 to slit-band. 



Dimensio)is. — Height of shell, nbout 16 mm.; widtli at mouth, about 15 mm. 



Horizon. — Middle Ordovician : Whitehouse Group. 



Localitij. — Shalloch Mill, Grirvan. 



Remarks. — The affinities of this species seem to be with Bucania lia.Ili, Ulrich 

 and Scof.,^ and probably with B. radiatn (Eichw.).'' It is dedicated to the famous 

 Scottish geologist, Playfair. 



4. Bucania cf. punctifrons (Emmons). Plate VI, fig. 11. 



One fragment of the dorsum of the outer whorl of a distorted shell shows an 

 ornamentation apparently identical with tliat of B. jiunctifrons (Emmons)* of the 

 Trenton Formation. The small oval pits on the surface seem formed by the 

 contact of fimbriated lamellose lines, and these pits appear to be arranged in 

 indistinct transverse lines inclined back to the narrow carina at about 45°. The 

 slit-band is not clearly visible, probably owing to the state of preservation and 

 slight crushing of the dorsum, but there is a narrow elevated ridge probably 

 representing it on the broad flattened back. 



^ Ulrich and Scofield, op. cit., p. 887, pi. Ixvi, figs. 1—3. 



2 Ihid., p. 886, pi. Ixvi, figs. 4—8. 



3 Kolven, ' Gastrop. Bait. Uutersil.,' p. 121, fig. 5. 



* Emmons, ' Geol. Rep., 2nd Distr., New York,' 1842, p. 392, fig. 5 {Bellerophon punctifrons) ; 

 Hall, ' PalsBont. N.Y.,' vol. i, p. 187, pi. \\ a, figs. 1 a — e ; Ulrich and Scofield, op. cit., p. 894, 

 pi. xlvii, figs. 41 — 44. 



