Vol. 62.] OMOSPIRA, LOPHOSPIRA, AND TUBRITOMA. 553 



the character of the lines of growth and sinus. Later on, 1 he states 

 that he is not satisfied with the systematic position of Omospira, 

 and that 



' if Scalites, Emmons, could be proved to possess the essential characteristics of 

 the Rapbistomidae, then we would have an undeniable link between Omospira 

 and Raphistoma? 



Miller 2 regards Scalites and Omospira as identical : they certainly 

 bear considerable resemblance to one another, but in Scalites the 

 upper part of the whorl is much flatter, which gives the spire 

 a step-like appearance, and the whorls are more angular at the 

 periphery. In general form, Omospira greatly resembles some 

 members of the Murchisoniidae and the Pleurotomariidas, especially 

 such a species as Hormotoma bellicincta, Hall, which possesses a 

 sinus. It is distinguished from the typical members of both 

 families by the usually greater relative width of the band, and also 

 by the character of the lines of growth. The lines of growth 

 above are continuous with those on the band, and increase in 

 curvature below, just before the angle, so that they do not form 

 even crescents on the band. In the Murchisoniidee and Pleuroto- 

 mariidae the lines of growth form uniform crescents on the band, 

 and in the true members of each family there is a definite break in 

 their continuity with those above and below. Prof. Koken 3 considers 

 that this genus resembles his Pseudomurchisonia, which, however, 

 differs by having the band on the anterior whorls only, and by the 

 lines of growth on the posterior whorls being merely sinuated. 



Range. — In America, according to Dr. Ulrich, Omospira occurs 

 in the Black-liiver and Trenton Formations, and may perhaps be 

 represented by a single form in the Upper Silurian. In Britain, I 

 am only acquainted with one species, 0. orientalis, sp. nov., from 

 the Upper Bala. 



Omospika orientalis, sp. nov. (PI. XLIII, figs. 1, 2, & 2 a.) 



Diagnosis. — Shell turreted, composed of about seven whorls. 

 Whorls increasing somewhat rapidly, angular near the middle of 

 the body-whorl and below the middle of the earlier whorls, slightly 

 convex above and below — except immediately above the angle, 

 where there is a broad flat band. The angle is not so sharp on the 

 earlier whorls, and the band is there seen to be bounded on each 

 side by a raised thread. This band represents the sinus in the 

 outer lip, which is broad and of moderate depth ; the base of 

 the sinus is not evenly concave, but recedes rather more below, 

 immediately above the angle. The lines of growth curve backward 

 to, and forward from, the band with a moderate degree of obliquity ; 

 they are distinct, and finer lines are intercalated between stronger 

 ones. The base is convex. There are traces on the body- whorl of 

 a very fine spiral thread a little distance below the angle. Aperture 

 unknown. 



1 Final Rep. Geol. & Nat. Hist. Surv. Minn. vol. iii, pt. ii (1897) p. 944. 



2 ' North American Geology & Palaeontology ' 2nd Appendix (1897) p. 769. 



3 ' Ueber untersilurische Gastropoden' Neues Jabrb. vol. i (1898) p. 15. 



2q2 



