FROM NORTHWESTERN EUROPE 31 
DIMENSIONS OF FIGURED SPECIMENS. 
length thickness width 
3°30 cm 2°35 cm 3°78 cm 
2°86 cm 2:20 cm 3°22 cm 
Internal characters. The internal characters have been investigated using material 
collected near Virieu-le-Grand (Ain) in the southern French Jura. Although not 
topotypic, the material is of the correct age and is not far from Trept (Isére), a 
locality mentioned by Oppel (1866) in his original description of the species. 
Pedicle valve. A well developed pedicle collar is present in adult specimens. The 
shell is massive and while lateral cavities are present they are of a very reduced 
nature and bounded by slender dental lamellae. Although the dental lamellae are 
very slight, the teeth are strongly supported by the thick shell wall. 
Brachial valve. There is a low median septum ; other characters as in generic 
description. 
DiIsTRIBUTION. The species appears to occur quite abundantly throughout the 
French and Swiss Jura and in Poland. That L. arolica has not been recorded from 
either the Swabian or Franconian Jura is attributed to the fact that the ‘‘ Sponge 
reef ’’ facies did not develop in that area until the lower Kimmeridgian. 
OccuRRENCE. The material collected by the author came from the Chavoley 
Beds (Ager & Evamy, 1963) near Virieu-le-Grand (Ain). These beds, consisting of 
calcareous marls and shales, represent the only argillaceous interruption in the 
succession of carbonate sediments which constitute the Upper Jurassic of the 
southern French Jura. The associated fauna included hexactinellid sponges and 
rare specimens of Monticlarella striocincta. L. arolica was the commonest element 
in the fauna and is also abundant in the “‘Birmensdorfer Schichten ”’ of the type area 
in Switzerland. 
Lacunosella vaga sp. n. 
(Pl. 2, figs. 1-3, text-fig. 14) 
1932 ?Septaliphoria pinguis (Roemer); Wisniewska: pl. 1, figs. 13, 14, NON figs. 1-11, 15-20. 
Name. Latin vagus-a-um: wandering, the species has a wide geographical 
distribution. 
Diacnosis. Medium-sized, symmetrical, sub-pentagonal Lacunosella ; beak 
small ; 16-20 subangular ribs ; no posterior smooth area ; crura falcifer. 
STRATIGRAPHICAL RANGE. Kimmeridgian—only accurately recorded from the 
upper mutabilis and lower pseudomutabilis zones. 
TYPE SPECIMEN. Holotype, no. BB. 44135, obtained from mutabilis zone at 
Sermérieu (Isére), France. 
DIMENSIONS OF HOLOTYPE. Length 2-69 cm, thickness 2-00 cm, width 3-02 cm. 
MATERIAL. 43 specimens from type locality ; 22 specimens Col du Chat (Savoie) ; 
28 specimens from Franconia. All except the figured specimens are in the author’s 
collection, British Museum (Nat. Hist.) nos. BB. 45668-73, BB. 45756-61. 
