220 MRS. JAJ5TE LONGSTAFF ON [May I909,. 



Loxonema plabtatum, sp. nov. (PL X, figs. 6 a & 6 5.) 



Diagnosis. — Shell composed of more than eight whorls. Whorls 

 smooth, increasing gradually, so closely adpressed at the suture as 

 to give rise to a flattened band, convex below. Lines of growth 

 distinct, fine with occasional stronger lines intercalated, sigmoidal, 

 more strongly curved on the body-whorl than on the whorls of the 

 spire, greatest sinuosity submedian. Sutures oblique. Base convex,, 

 somewhat produced. 



Remarks and resemblances. — All the specimens of this 

 species known to me are so greatly compressed that the whorls 

 appear wider than they must originally have been. The depth and 

 height of the sinus vary slightly on different individuals. The 

 specimen figured in PL X, fig. 6 b, has the sinus on the body- whorl 

 rather deeper than that on any of the others. L. planatum is 

 distinguished from L. sinuosum (Sow.) by the whorls being more 

 flattened and more adpressed at the suture above ; by the lines of 

 growth being less sharply bent near the middle of the whorl ; and 

 by a more marked difference in the amount of this sub-central 

 bend on the body- whorl from that on the whorls of the spire. It 

 somewhat resembles L. latouchei ; but it is shorter, and the lines of 

 growth are different. 



Dimensions. — The holotype (G 4656) figured (PL X, fig. 6 «)■ 

 is in the British Museum (Natural History). It consists of four 

 whorls and the impression of four others, in a length of 28 milli- 

 metres ; the greatest width is 13 mm., but measured in the opposite 

 direction it would be much less, on account of the pressure to which 

 the shell has been subjected. The example in the Oxford University 

 Museum (fig. 6 b), of which portions of the penultimate and body- 

 whorls are reproduced, consists of only these two whorls which 

 are 18 mm. in length ; the greatest width is 14 mm., and in the 

 opposite direction it is only 6 mm. on account of the specimen being 

 compressed. A fragment which is in Sir Charles Holcroft's collection 

 must have been part of a much larger shell ; it consists of three 

 whorls, which have a total length of 38 millimetres. 



Locality and horizon. — There are two specimens (Gr 4637 

 & 4656) in the British Museum (Natural History) and two in the 

 Oxford University Museum, all from the Wenlock of Garcoed, Usk, 

 Monmouth. The latter Museum also contains two examples 

 from the Upper Ludlow, and an obliquely compressed shell which 

 is probably this species from the Lower Ludlow of Ledbury. In 

 the Museum of Practical Geology, Jermyn Street, there are three 

 specimens (Xos. 21064, 21065, & 21068) from the Lower Ludlow 

 of .Ledbury and two (Xos. 21072 & 21073) from the Upper Ludlow 

 of the River Wye near Erwood, but none of these are well preserved. 

 The Worcester Museum contains two very imperfect shells collected 

 by the late Mr. G. Reece, each consisting of about two and a half 

 whorls, from the ' Woolhope or Wenlock Shale Series ' of the 

 Malvern Hill Tunnel, which probably belong to this species. 

 Mr. Madeley has a specimen which is more like this species than 

 any other : three whorls are partly visible, and the lines of 



