200 E, Wilson — British Liassic Gasteropoda. 



Trochus Nioktensis, D'Orb. PI. V. Figs. 6, 6a, 66. 

 1850. D'Orb. Pal. Franc. Ter. Jur. vol. ii. Gast. p. 282, pi. 315, figs. 5—8. 



I recently obtained a little shell from the Marlstone Eock-bed of 

 Downcliff, near Bridport, Dorset, which in all essential respects 

 agrees with Tr. Niortensis, described by D'Orbigny as having been 

 derived from the etage bajocien (Inferior Oolite) of Niort (Deux 

 Sevres). 



^ Description. — The following is a translation of that author's descrip- 

 tion : — "Shell conical, much longer than broad, imperforate. Spix'e 

 formed of a regular angle, composed of whorls very much hollowed 

 out, striated longitudinally, and marked in the lower portion with 

 oblique cost^ tuberculated below {i.e. posteriorly). The last whorl 

 is convex, striated concentrically above and angular over the sides. 

 Aperture a little depressed and angular. Spiral angle, 49°. Length, 

 10 mm. ;_ breadth, 8 mm." (D'Orbigny, Pal. Fr. I.e. p. 282). 



Affinities. — My specimen has a less elevated spire than D'Orbigny's 

 type, being only a little higher than broad, 6 : 5, with a decidedly 

 greater spiral angle, viz. 60° ; the three apical whorls and the spiral 

 angle are a little convex ; the costee, too, are more strongly nodulated 

 at their anterior ends and prominent on the upturned keel ; the base 

 shows radial as well as encircling striee; and the aperture is more 

 squarely angulated than in D'Orbigny's figure. These differences 

 are of detail rather than of essence, and not more than might 

 reasonably be expected between individuals of the same species 

 derived from such widely-separated horizons as the Middle Lias and 

 the Liferior Oolite. D'Orbigny speaks of the aperture of his Tr. 

 Niortensis as " angular," and in this the description is probably more 

 correct than the delineation, which, like that of too many of the 

 figures in the Paleontologie Fran9aise, appears to have received an 

 artistic rounding off or restoration not strictly true to nature. 



Ohs. — The occurrence of this fossil in the English Lias is of special 

 interest from its being one of those that range into the Oolite. 



Geological Position and Locality. — Middle Lias, Conglomeratic 

 Marlstone, zone of Am. spinatus, Down Cliff, near Bridport, Dorset. 



Ambekleya Callipygk, spec. nov. PL V. Figs. 7, 7a. 



Description. — Shell turbinate, thin, imperforate; spiral angle 

 regular ; whorls 6-7, only slightly convex, the greatest diameter of 

 the whorl is attained a little behind the anterior suture, whence it 

 falls rapidly thereto, thus giving a slight tabulation ; sutures narrow, 

 but clearly defined ; last whorl relatively large, long and inflated ; 

 base very convex ; aperture broadly ovate ; outer lip thin, with its 

 inner margin very finely crenated ; inner lip slender, extending 

 somewhat over the columella, vertical, but arching forwards towards 

 its angular junction with the outer lip at the anterior margin, which 

 at this point is patulous and a little effuse. The ornamentation of 

 this handsome shell is elaborate, the whole surface being covered 

 with close-set spirals of small rounded tubercles. On the first 

 4-5 whorls these granular tubercles are much finer than on the 



