LIOCERAS V-SCRIPTUM. 71 



v-scriptum, becoming gradually sufficiently pronounced to constitute a definite 

 species. 



Lioc. v-scriptum has some resemblance to Lioc. fallax, under which heading the 

 differences are mentioned. It has also much resemblance in general shape to 

 Lioc. giganteum ; but the differences consist in the ribs being coarse and V-shaped, 

 instead of fine and sigmoidal, the carina less prominent, and the umbilicus regularly 

 concave. As regards the latter character, a complete examination of Lioc. concavum 

 and all its varieties indicates that an almost entirely concave umbilicus is a most 

 constant feature in the adult. 



Lioc. v-scriptum is a somewhat common form in the Concavum-beds of Bradford 

 Abbas, Dorset. I have no specimens actually labelled " Halfway House," though 

 I have little doubt it occurs there. A small specimen from Stoford, Somerset, 

 is in my collection, and another labelled "East Coker" in that County. This 

 latter specimen would seem to indicate that some trace of the Concavum-beds is 

 represented in the quarry there. 



Plate IX, fig. 1, represents an adult specimen of the middle form of Lioc. 

 v-scriptum, showing the termination of the mouth-border. The greater portion of 

 the test is present, and fairly well preserved. A portion of the sutures is shown 

 in situ (fig. 4) ; and the cross indicates the commencement of the body-chamber. 

 The other side of this same specimen was figured in my father's memoir 1 ; and fig. 3 

 illustrates a portion of this view of the specimen, which is without the test, and 

 thus shows the constrictions. My father supposed 2 that this specimen possessed 

 a long lateral process, but I can see no indication of it ; and the termination, as 

 indicated by the fine lines of growth, is perfectly complete on the side shown 

 in my fig. 1. Fig. 2 gives the front view of the same specimen. The test is 

 absent on the top ventral area of the body-chamber, and should have been so shown 

 in fig. 1 just along the edge, thus accounting for the depression towards the top of 

 the mouth of fig. 1 . The slight increase in the thickness of the upper portion of 

 the body-chamber towards the termination causes the concavity on the inner area 

 to appear more pronounced. This specimen was collected by my father at Brad- 

 ford Abbas. PI. X, figs. 7, 8, exhibit what may practically be taken as a young form, 

 the only difference being a slight tendency to increase the diameter of the umbilicus 

 rather more than in the true young forms. Otherwise this form shows the characters 

 and proportions very well, especially the small carina and the V-shaped ribs. It 

 was chosen for figuring to compare with Lioceras apertum (PI. X, figs. 10, 11). 

 This specimen is from Bradford Abbas. PL IX, fig. 7, illustrates a really young 

 specimen of the middle form with the lateral process as developed in youth. 

 This process is shorter and more pointed than that met with in Lud. cornu. (It 



1 ' Quart. Journ. Geol. Soc.,' xxxvii, p. 60. 



2 Loc. cit. 



