Vol. 62.] OMOSPIRA, LOPHOSPIRA, AND TURRITOMA. 561 



suture. Band trilineate, situated 011 the angle. Lines of growth 

 curving very obliquely back to the band above and forward again 

 below. Sinus in the outer lip triangular, of moderate depth. 

 Base convex and but slightly produced. Indications of an open 

 umbilicus. Test thin. 



Remarks and Resemblances. — There are four specimens of 

 this species in Mrs. Gray's collection; and also a fifth example 

 which I am placing with them for the present, as it greatly resembles 

 them, more especially in the form and obliquity of the lines of 

 growth : the surface is, however, not well-preserved and it is much 

 bigger, so it is difficult to be certain of the correctness of the 

 identification. The discovery of better specimens may prove this to 

 be a distinct species, while, on the other hand, if a larger series 

 were found, some might be intermediate in size and prove to be 

 connecting-links with the type. Two of the specimens are repre- 

 sented by both internal and external moulds. The internal mould 

 of one of these is figured in PI. XLIII, fig. 8 ; the band has a very 

 sharp keel on the body-whorl, and the bordering keels are only 

 faintly seen on a portion of it ; but the three keels are clear on the 

 penultimate whorl, and they are still more distinct on a wax- 

 impression of this whorl taken from the external mould, where the 

 band is wider and the three keels nearly equal in strength. On this 

 shell the base of the sinus in the outer lip appears to be intact, and, 

 judging by the lines of growth, it was probably not originally much 

 deeper than is now represented. The other three examples all show 

 the trilineate band ; on one of them (PL XLIII, fig. 9) it is not quite 

 so wide, and the central keel is more prominent. The largest specimen 

 (PI. XLIII, fig. 10) has the three anterior whorls represented by the 

 internal mould, and the posterior ones by the external impression 

 in the matrix. The band is not well-preserved on the body-whorl, 

 where it is a prominent ridge, and the bordering keels are faint. 

 On the third whorl from the base the central keel alone appears, and 

 it is sharp and flange-like. The American species which this most 

 nearly resembles is L. perforata, Ulrich * (Murchisonia bicinctaf, 

 Meek & Worthen non Hall), but the figures do not give the surface- 

 structure well enough to make a satisfactory comparison. 



Dimensions. — The specimen figured in PL XLIII, fig. 10, 

 consists of about six whorls, and has a length of 16 millimetres and 

 a width of 13 mm. That represented by fig. 8 in the same plate is 

 imperfect, and consists of about one and a half whorls, which 

 = 8 mm. in length and 10 mm. in width. The wax-impression of 

 this same shell gives three whorls, which = 7*5 mm. in length 

 and 10 mm. in width. That represented by fig. 9 in PL XLIII 

 = 12 mm. in length and 8 mm. in width. 



Locality and Horizon. — Four of the specimens, including 

 those figured, are from the Upper Bala [Lapworth] of Thraive Glen 

 (Ayrshire). The other is from the Starfish Bed, which is of the same 

 age, and occurs in the same locality. 



1 Final Eep. Geol. & Nat. Hist. Surv. Minnesota, vol. iii, pt. ii (1897) 

 p. 984 & pi. lxxiii, figs. 32-35. 



