Vol. 62.] OMOSPJBA, LOPHOSPIRA, AND TURRITOMA. 563 



forward again below. There is an additional and slighter keel below 

 on the body- whorl, which is partly visible above the snture on 

 some of the earlier whorls ; traces of fine spiral lines are also 

 evident on the surface. Aperture and apex unknown. 



Remarks and Resemblances. — Mrs. Gray's collection con- 

 tains but one specimen, and its surface is only imperfectly preserved. 

 I know of no other species which it resembles. It probably belongs 

 to the Cicelia subsection, though it is hardly so slender as the other 

 members of the group. 



Dimensions. — Length = 9 millimetres; width = 4*5 mm. 



Locality and Horizon. — Ardmillan Brae (Ayrshire), in beds 

 of Llandeilo age [Lapworth]. 



B. Bicincta Section. 

 Bicincta Subsection. 

 Lophospira. bicincta (Hall). (PI. XLIY, fig. 2.) 



Murchisonia bicincta, J. Hall, 1847, ' Pal. New York ' vol. i, p. 177 & pi. xxxviii, 

 figs. 5 a-6f (?5ff&5h); non F. M'Coy, 1846, ' Syn. Silur. Foss. lrel.' p. 16 

 & pi. i, fig. 17 ; non J. W. Salter, 1859, Geol. Surv. Can. ' Canadian Organic 

 Rem.' dec. i, p. 19 & pi. iv, figs. 5-6 ; non Meek & Worthen, 1868, Geol. 

 Surv. 111. vol. iii, p. 317 & pi. iii, fig. 4. Murchisonia Milleri, J. Hall, 1877, 

 Miller's 'Amer. Pal. Foss.' 1st ed. p. 244; non Pleurotomaria bicincta, G. 

 Lindstrom, 1884, 'Silur. Gastrop. & Pterop. Gotl.' Kong). Svensk. Vet.-Akad. 

 Handl. n. s. vol. xix, no. 6, p. 106 & pi. viii, figs. 15-25. Lojphospira bicincta, 

 E. O. Ulrich, 1897, Final Rep. Geol. & Nat. Hist, Surv. Minnesota, vol. iii, 

 pt. ii, p. 964 & pi. lxxii, figs. 1-5. '{Murchisonia bicincta, J. Home & B. N. 

 Peach, 1899, Mem. Geol. Surv. ' Silur. Rocks of Hritain ' vol. i. pp. 682 & 695. 

 Pleurotomaria Milleri ■= PL bicincta, ? E. N. Peach, J. Home, & A. Mac- 

 conochie, 1901, in ' Fauna, Flora, & Geology of Clyde Area ' publ. by Local 

 Comm. for Meeting of Brit. Assoc. Glasgow, p. 439. 



Diagnosis. — Shell turbinate, consisting of more than four 

 whorls. Whorls increasing somewhat rapidly, angular above the 

 middle of the body-whorl and near the middle of the earlier whorls, 

 more concave above the angle than below. Sinual band situated on 

 the angle, narrow, trilineate, the central keel sharp and prominent, 

 the two bordering threads finer. Lines of growth sharp raised 

 threads, curving back to the band above, with a moderate degree of 

 obliquity, almost vertical below. Ornamentation consisting of a 

 strong keel placed below the suture about a third of the distance 

 between it and the band, and another keel at about the same 

 distance from the band below. Body-whorl not much produced. 

 Base convex. Aperture subcircular. 



Remarks and Resemblances. — There are two specimens in 

 Mrs. Gray's collection which appear to be this species. I have not 

 had the opportunity of seeing any of Hall's specimens ; therefore, in 

 identifying the Scottish shells, I am guided to a certain extent by his 

 figures and description, but more especially by Dr. Ulrich's figures 

 and remarks thereon, as he has had the opportunity of examining a 

 large series of American examples. Dr. Ulrich considers that Hall 

 has united more than one species or variety under the name bicincta. 

 The figures evidently differ from one another. Dr. Ulrich therefore 

 sets aside figures 5 g & 5 h on pi. xxxviii, and regards 5 a-bf as 



