MURCHISONIA. 61 



It may be noticed that the sutural angle varies considerably, the spire having 

 been imperfectly coiled as often happened in M. turbinata. 



3. MuRCHisoNiA siMiLis, Trenhuer. Plate V, figs. 22 — 23 a. 



1867. MtTECHisoNiA SIMILIS, TrenJcner. Palaont. Novitat., pt. 1, p. 10, pi. i, 



fig. 17. 



1868. — QTTADEiciNCTA, Trenkner. Ibid., pt. 2, p. 22, pi. vii, fig. 10. 

 1884. — BiM.w.m, Clarke. Neues.Tahrb. f. Min., Beil.-BandS, p. 346, 



pi. V, fig. 14. 

 1893. — sp., Tschernyschew. Mem. Com. Geol., vol. iv, pt. 3, p. 38, 



pi. 3, fig. 12. 



Description. — Shell very small, elongate, conical, turrited, of seven or eight 

 slowly increasing whorls. Apex sharp. Sutures simple, rather shallow. Whorls 

 rather narrow, convex, much exposed. Ornament consisting of a fine elevated crenu- 

 lated thread immediately below the suture, two other threads bounding the sinus- 

 band, which lies just below the centre of the back, and a fourth thread not quite 

 half-way from the sinus-band to the lower suture ; the whole crossed by micro- 

 scopical, close and regular, transverse lines, which are nearly straight, and slope 

 very obliquely backward from the sutures, and then arch to meet on the sinus- 

 band. Body-whorl possibly rather larger than the others. Umbilicus apparently 

 shallow and concave. 



Size. — A specimen retaining the four lowest whorls is 5 mm. high by 2 mm. 

 wide. 



Localities. — There are five specimens (moulds) from Vicarage Well, Pilton, in 

 the Barnstaple Athenaeum. 



Remarks. — The three lower longitudinal threads divide the whorl into four 

 bands, and are so placed that the two central bands, the upper of which is the 

 sinus-band, are rather narrower than the upper, and sometimes than the lower, 

 marginal band. The transverse ornament is very minute, and only visible in good 

 lights. I did not observe it till after the figures were drawn, and, in fact, it is 

 too fine to be represented in them. It is, however, very regular and definite, and 

 proves the shell to belong to Murchisonia. 



Our specimens appear to agree with Trenkner's figure of M. similis, but to be 

 less aciculate than the fossil given by him as M. quadricincta, and refigured by 

 Clarke. The latter name has been applied by Pacht ^ to another small species 

 which is perhaps distinguished by being shorter, by having more angular whorls, 

 and by a different arrangement of the longitudinal threads. 



1 1854, Pacht, ' Dev. Kalk. Livland,' p. (295), plate, fig. 1; aud 1858, Pacht, iu Baer and 

 Helmersen's ' Beitr. Buss. Reiches,' vol. xxi, p. 101, pi. v, figs. 9 «, b. 



