E. Wilson — British Liassic Gasteropoda. 201 



last 2. The third whorl bears only 4 of these spirals. The 

 penultimate whorl bears 7 granular spirals ; of these the sixth 

 from the posterior suture lies on and determines a faint angle, and 

 the seventh is close to the anterior suture; these two rows consist 

 of rather coarser tubercles, and speaking generally the granules get 

 smaller towards the posterior suture ; the spirals are separated by 

 about their own breadth from one aiiother, and the individual beads 

 of a spiral from a little less up to rather more than their own width. 

 On the last whorl very finely granulated lines are seen setting in 

 between the rows of coarser granules ; there are eight or nine of each 

 series counting from the periphery, whilst the base shows a like 

 number of the coarser spirals (which are more closely set and 

 somewhat finer than those posterior to the peripher'y), with indica- 

 tions of fine alternating spiral lines. 



Dimensions. — Length, 8 millimetres ; diameter, 5'75 mm. ; length 

 of last whorl, 5-75 mm.; spiral angle, 68^^; sutural angle, 125°. 



Geological Position and Locality. — Middle Lias, zone of Am. 

 margaritatus, Daventry, Northamptonshire. 



MoNODONTA (Turbo) humilis, spec. nov. PI. V. Figs. 8, 8a, 8&. 



Description. — Shell small, smooth, spire greatly depressed ; whorls 

 4, flattened and embracing, with linear sutures and scarcely exsert 

 (Fig. 8), but occasionally the whorls are a little convex, the sutures 

 distinct, and the spire slightly raised (Fig. 8a). A shallow sulcus 

 encircles the whorls posteriorly; this depressed area is most apparent 

 on the last whorl, and occasionally becomes so mai'ked as to hollow 

 out its whole upper surface, and give an angulated instead of the 

 prevailing obtusely rounded border to the shell ; the columella is 

 very short and twisted, it terminates by uniting with a prominent 

 bluntly triangular tooth, which originates at the edge of the inner 

 lip in advance of and reflected over the minute umbilicus. Aperture 

 transversely ovate, rather small and not quite continuous, directed 

 obliquely forwai'ds, and having its outer border slightl}' constricted 

 by the sulcus. Base almost flat, very slightly convex, more or less 

 wrinkled towards the centre. Under a lens the shell shows numerous 

 close-set lines of growth. 



Dimensions. — Height, 2'50 millimetres. Diameter 3 mm. 



Geological Position and Locality. — Lower Lias, zone oiAm. oxynotus, 

 common in the Tunnel waste heaps. Old Dalby, Leicestershire. 



MoNODONTA (TuKBo) LiNDECOLiNA, spec. nov. PL V. Figs. 9, 9a, 96. 



Description. — Shell small, thick, transversely ovate; imperforate; 

 spire scarcel}' exsert, and apex obtuse ; whorls 5-6, convex, embracing 

 with scarcely visible linear sutures, the last whorl inflated ; a shallow 

 sulcus bounds the posterior suture; base slightly convex; the umbilical 

 region, which appears to be covered by a thin shelly callus, is 

 encircled by a more or less prominent semicircular ridge which runs 

 nearly from the posterior to the anterior inner margin of the aperture ; 

 aperture almost exactly circular, oblique, the last whorl slightly 



