﻿262 



EOCENE MOLLUSCA. 



Nec Pleukotoma undata. Bast. 1825. Mem. Geol. sur les Env. de Bordeaux, p. 64, No. 7. 

 nec — — V. Hauer. 1837. Fossth. imtert. Becken v. Wien. Jahrb., p. 419, 



No. 98. 



nec — — Grat. 1838. Cat. Zool., &c, du Bass de la Gironde, p. 46, No. 394. 



nec — — Grat. 1840. Conchyl. foss., &c, du Bass, de l'Adour (Atlas 



Pleurot., t. 2, fig. 36). 



P. testa elongato-fusiformi, sub-turritd, lineis spiralibus costulisque longitudinalibus 

 ornatd: spird acuminata: anfractibus convexiusculis, postice sub-canaliculatis ; lineis 

 concentricis crassiusculis, depressis, numerosis, undatis ; costulis undatis, variis : aperturd 

 angusto-ovatd, antice in canali brevi exeunti j labro tcnuissimo, arcuato ; sinu latiusculo, 

 narginibus sub-parallelis, anticd in margine collocato. 



Shell oblong, fusiform, somewhat turreted, ornamented with spiral lines and 

 longitudinal ribs ; the spire pointed, produced, always exceeding the last whorl in 

 length ; whorls eight or nine (exclusive of a smooth, conical pullus of three volutions), 

 convex, short, and bluntly angular on the shoulders. The posterior margins are 

 slightly channelled ; the sutural edges, in the young shells, are frequently bordered by a 

 single row of small, roundish tubercles, which disappear on the fourth or fifth whorl, 

 and the edges then become feebly and distantly crenulated, or they present three or 

 four prominent, thread-like lines. The concentric lines are numerous, irregular, fine 

 and thread-like over the margins, rather thick and depressed over the middle and 

 front parts of the whorl, and slightly wavy on the last whorl ; the longitudinal ribs 

 are short, oblique, curved, and very variable in different specimens, both in size and 

 number, sometimes being moderately large and distant, sometimes small and crowded. 

 The aperture is of an oblong-oval form, and terminates in front in a short, somewhat 

 narrow, and nearly straight canal ; the outer lip is very thin, much arched, and 

 expanded towards the middle ; the sinus is moderately wide, deep, with nearly parallel 

 margins, and placed in the very front of the margin, immediately behind the shoulder. 



The transverse lineation in the English specimens is, as is not unfrequently the 

 case, of a coarser character than that found in the French shells ; and there is also a 

 slight difference in the condition of the posterior margins. These variations, however, 

 do not appear to be of sufficient importance to justify the separation of the English 

 shells. 



Size. — Axis, 1 inch and 2-12ths (30 millim.); diameter, nearly 5-12ths of an inch 

 (10 millim.). 



Localities. — Stubbington ; French: Grignon, Parnes, Mouchy, Courtagnon (fide 

 Desk.), Saint-Felix, Ully-Saint-Georges (fide Graves), la Vallee de l'Aisne (fide 



Melleville) . 



