jE. Wilson — British Liassic Oasteropoda. 197 



a roundly- furrowed instead of a sharply-ribbed base, and an apparent 

 and large umbilicus. 



Note. — Trochus Thetis seems to be a difficult form to delineate. It 

 has several times been re-figured, but never drawn with perfect 

 accuracy. The figures I give (PL V. Figs. 2, 2a, h, c) are an advance 

 on most of the previous figures, but the appearance of an umbilicus 

 is fallacious. 



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

 oxynotus, Railway-tunnel, Old Dalby, Leicestershire. 



Trochus Cricki, spec. nov. PI. V. Figs. 3, 3a, 3h. 



Description. — Shell conical, imperforate ; spiral angle regular, very 

 slightly concave, apex acute ; whorls 5-6, quite flat; sutui'es linear, 

 only slightly inclined ; last whorl obtusely angulated at the circum- 

 ference ; base almost flat, very slightly convex ; columella pi'ominent, 

 massive and vertical ; outer lip imperfect, but the aperture when 

 complete appears to have been rhomboidal and only a little wider 

 than high. The whorls are covered with close-set spirals of small 

 rounded tubercles, the spiral lines and the individual tubercles being 

 respectively closer together than their interspaces ; on the penultimate 

 whorl there are 5-6 spirals ; the tubercles of the most anterior row 

 of these are a little the largest, and give a slight tabulation to the 

 whorls, the row next behind are nearly equally large, then there is a 

 very fine row, and behind these two rather coarser rows ; on the last 

 whorl 4 rows of coarser tubercles occupy the angular border, 

 posterior to which are 4 rows of finer tubercles ; on the base im- 

 mediately within the 4 coarse granular lines are 3 finer lines, of 

 which the outer one only is granular; the rest of the base is smooth. 



Dimensions. — Length, 5 millimetres ; diameter, 4 mm. ; length of 

 last whorl, 3'25 mm. ; spiral angle, 65°; sutural angle, 130'^. 



Affinities. — This small shell appears to have rather close affinities 

 with certain small Oolitic Trochi having gi-anulated spires and smooth 

 bases, such as Tr. monilitectiis, Phil., and its allies Tr. Scarburgensis, 

 Hudl., and 2r. strigosus, Lye, figured and described by Mr. W. H. 

 Hudleston, M.A., F.K.S., in his "Palaeontology of the Yorkshire 

 Oolites" (Geol. Mag. Dec. IIL Vol. IL 1885, p. 121, et seq.). It 

 does not, however, appear to be absolutely identical with any of these. 



Ohs. — I name this fossil after Mr. W. D. Crick, of Northampton, 

 whose valuable work on the pala3ontology of the Lias of that district 

 has already been acknowledged. 



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

 garitaius, Daventry, Northamptonshii'e. 



Trochus sagenatus, spec. nov. PI. V. Figs. 4, 4a. 

 Description. — Shell conical, turrited, imperforate ; spiral angle 

 regular; whorls 8 probably (the apex being lost in my sole 

 specimen), a little concave and slightly imbricating. Each whorl 

 bears 3 equidistant encircling raised lines one a little in advance of 

 the posterior suture, the second a little in front of the middle of the 

 whorl, and the third forming a slight keel directly overhanging the 



