Vol.62.] OMOSPIRA, LOPHOSPIRA, AND TVRRITOMA. 557 



described in America. Dr. Ulricb states that they range from the 

 Calciferous to the Hamilton Group, and considers that the genus 

 attained its maximum of development in the Trenton Period. Ten 

 Silurian species from Gothland, described by Lindstrom as Murchi- 

 sonia or Pleurotomaria, have been referred by Ulrich to Lophospira. 

 MM. D.-P. (Ehlert describe and figure one species, namely L. brevi- 

 culus, 1 from the Devonian of the Mayenne. 



A. Perangulata Section. 

 Perangulata Subsection. 

 Lophospira gyrogonia (M'Coy). (PI. XLIII, figs. 3-5.) 



Murcliisonia gyrogonia, F. M'Coy, 1852, Ann. & Mag. Nat. Hist. ser. 2, vol. x, 

 p. 192 ; 1852, ' Brit. Paheoz. Foss.' p. 293 &pl. iK, fig. 43 ; 1854, ' Contrib. Brit. 

 Pal.' p. 243 ; J. Morris, 1854, ' Catal. Brit. Foss.' 2nd ed. p. 259 ; J. Sowerby, 

 1867, 'Siluria ' 4th ed. p. 197, Foss. 40, fig. 6, & Appendix p. 532; J. J. Bigsby, 

 1868, ' Thes. Silur.' p. 158 ; J. W. Salter, 1873, ' Catal. Carabr. & Silur. Foss.' 

 p. 69 ; A. C. Ramsay, 1881, Mem. Geol. Surv. vol. iii, ' Geol. N. Wales ' 2nd ed. 

 pp. 404, 414, & 431 ; J. D. La Touche, 1884, ' Geol. of Shropshire ' p. 59 & pi. v, 

 fiq-. 96; R. Etheridge, 1888, ' Foss. Brit. Is.' vol. i (Palaeozoic) p. 113; H. 

 Woods, 1891, ' Catal. Type Foss. Woodwardian Mus.' p. 107 ; J. Home & 

 B. N. Peach, 1899, Mem. Geol. Surv. ' Silur. Rocks of Britain ' vol. i, p. 682, 

 non pp. 699 & 706 ; J. Home, B. N. Peach, & A. Macconochie, 1901, in ' Fauna, 

 Flora, & Geology of the Clyde Area,' publ. by Local Comm. for Meeting of 

 Brit. Assoc. Glasgow, ? p. 428, non p. 438. 



Diagnosis. — Shell rather small, turreted, composed of more than 

 four whorls. Whorls angular, increasing somewhat rapidly, flattened 

 or slightly convexo-concave above, concave below, more or less irregu- 

 larly coiled, often exsert, last whorl showing a tendency to become 

 detached, sutures frequently very oblique. Sinual band situated on 

 the angle, above the middle of the body-whorl, sub-median on the 

 penultimate whorl; sharp, prominent, almost flange-like, composed 

 of three fine keels. Lines of growth forming distinct threads, 

 strong lines being intercalated between fine ones at tolerably regular 

 intervals, curving obliquely back to the band above and forward 

 below. Ornamentation consisting of a keel on the base at a little 

 distance below the band, which appears above the suture on the 

 higher whorls, when they are exsert ; and there are traces of a 

 very fine thread just below the upper suture. Umbilicus closed. 

 Aperture imperfectly known. 



Remarks and Resemblances. — There are nine specimens of 

 this species in the Sedgwick Museum, Cambridge, which are all 

 internal moulds. One of them is marked as M'Coy's type ; it has 

 the sutures very oblique and the whorls exsert. Another example 

 from the same locality has the sutures less oblique, and there is a 

 slight breakage along the sinual band which gives the appearance 

 of a deep slit in the outer lip, but this has not really existed in the 

 natural state, though the original sinus may have formed a line of 

 weakness which led to the breakage in this part. M'Coy's figure 

 seems to have been constructed from these two individuals : for it has 

 the slit represented on it, and rather more of the base is given than 



1 Bull. Soc. £tud. Sci. Angers, 1887 (sep. cop.) p. 22 & pi. viii, fig. 5. 



