Yol. 62.] OMOSPIBA, LOPHOSPIRA, AND TUBRITOMA. 555 



angle bears the band, which is prominent and frequently trilineate. 

 This band represents a sinus in the outer lip of greater or less 

 depth, which is never prolonged into a slit. The lines of growth 

 curve back to the band above, and forward again below. On it 

 they frequently differ from those above and below, being either 

 stronger or slighter, farther apart, or closer together. Aperture 

 subquadrate, usually longer than wide. The inner lip is generally 

 thickened, often slightly twisted, turning around the umbilicus so 

 as to form a kind of hollow pillar. Ornamentation consisting of 

 keels, sometimes with fine spiral lines in addition. 



Remarks and E-esemb lances. — The character which chiefly 

 distinguishes LopJiospira from both Pleurotomaria and Murcliisonia 

 is the possession of a sinus, instead of a slit, in the outer lip. This 

 feature also separates it from Wortlienia, which it otherwise greatly 

 resembles. The band representing the sinus may consist of a 

 blunt edge only, though it is generally trilineate, the central keel 

 being usually the strongest ; and it may be developed into a thin 

 undulating flange as in L. serrulata, Salt., but sometimes the 

 three keels are nearly equal. The lines of growth on the band 

 may be simple threads of varying degrees of strength, or they 

 may be imbricated, or again they may have a medium incision. 

 Dr. Ulrich 5 considers that Lophospira has the most primitive type 

 of sinual band, and that the genus 



'is the oldest of the many types strictly belonging to the family Pleuroto- 

 mariidae. We say this not so much because the genus goes far back in geological 

 time, for, according to known facts, several other types are equally ancient, but 

 because it shares characters with types belonging to other families which, 

 like the Pleurotomariidse, originated somewhere in the interval between the 

 Calcif'erous and the Upper Cambrian.' (Op. cit. p. 962.) 



He further states that the 



' simplicity of the band and apertural notch allies the genus with the 

 Euomphalidse.' 



Some species of LopJiospira bear a close resemblance to those 

 members of TrocJionema where the lines of growth are deflected 

 so as to form an apertural notch ; but Lophospira is always 

 distinguished from that genus by possessing a distinct band. 

 The species of LopJiospira vary one from the other in the height 

 of the spire, some being considerably elongated, while others are 

 quite short ; there is also a difference in the depth of the sinus, and 

 in the degree of obliquity of the lines of growth. Dr. Ulrich has 

 therefore divided them into four sections, and two of these again 

 into several subsections, which he names from characteristic 

 species (op. cit. pp. 962-964). These are : — 



A. Pbrangulata Section. — Apertural notch > -shaped, deep and wide, the 

 lines of growth sweeping strongly back to the sinual band above and 

 forward again below. 

 1. Perangulata Subsection. — Shells not very high ; whorls five to eight, 

 strongly angular. Type, LopJiospira perangulata, Hall. 



1 Final Kep. Geol. & Nat. Hist. Surv. Minnesota, vol. iii, pt. ii (1897) p. 950. 



