E. Wilson — British Liassic Gasteropoda. 261 



Description. — Shell tnrrited, fusiform ; spiral angle regular ; 

 wliorls 9 or thereabouts, convex, very feebly carinated a little anterior 

 to the middle line, and ornamented by several fine spiral threads of 

 unequal thickness. In one specimen (Fig. 14), which is the more 

 complete of the two, but is imbedded in the rock so as not to show 

 the aperture, there are on the penultimate whorl 11-12 threads. Of 

 these four are coarser than the rest ; two of those which are most 

 prominent and subcentral in position determine the faint keel ; the 

 other two are anterior to these ; between the second and third, and 

 also between the third and fourth, of these coarser threads, counting 

 from the anterior suture, there is a fine line ; posteriorly to the fourth 

 coarse thread there are two threads of medium coarseness with a fine 

 thread between them, and there are two or three more fine threads 

 between the last of these and the posterior suture. Crossing these 

 are numerous inconspicuous curved radial lines of growth. The 

 earlier whorls are badly preserved, but enough remains to show that 

 they bear strong straight radial costee ; these costee disappear on the 

 later whorls, and there are no signs of them on the last two or three. 

 The canal-sheath, uniformly slender from its origin, is prolonged in 

 a straight line axially to its termination ; it is striated bj' fine oblique 

 lines. (In Piette's type the canal was broken off short, so that the 

 character of its termination could not be given.) The aperture and 

 ultimate wing (I'aile definitive) are not shown, but the character of 

 the latter is indicated by a single longish slender spine, which 

 originates from the posterior line of the keel, making an angle of 

 68° with the axis of the spire. 



Dimensions. — Height, including the canal, 19 mm. ; height, without 

 the canal, 14 mm. ; greatest breadth of last whorl, exclusive of the 

 wing, 8 mm. ; spiral angle, 25°; sutural angle, 115°. 



Geological Position and Locality. — Upper Lias, zone of ^m. serpen- 

 tinus, Burrow Hill, between Dodtord and Norton, Northamptonshire. 



The other specimen (Fig. 15) is much less perfect, but it agrees 

 pretty closely with the foregoing in its general form and ornamenta- 

 tion. The whorls, however, appear to be more convex, with deeper 

 sutures, and are even less perceptibly carinated ; they are crossed by 

 widely spaced slender curved radial costte, which taper away towards 

 the sutures, and almost disappear on the later whorls ; a short spinous 

 process remains at the opposite side to the aperture, from which 

 point a single angular and moderately prominent keel is continued 

 forwards : the base as well as the apex of the shell having suffered, 

 considerably, we cannot say for certain whether any more spinous 

 processes were developed on the keel or what were the characters of 

 the canal and the wing. 



Dimensions. — Spiral angle, 25°; sutural angle, 120°. 



Geological Position and Locality. — Upper Lias (transition-bed to 

 Middle Lias), Chipping Warden, Northamptonshire. 



Obs. — There are minor differences in form, and in the number 

 and arrangement of the spiral lines, between the above shells 

 and between each of them and Piette's figure of Alaria semi- 

 costulata. The shell from Burrow Hill (Fig. 14) evidently does not 



