1853.] MORRIS — LINCOLNSHIRE OOLITES. 343 



Phasianellapahidiniformis, Buvignier, which in other respects it nearly 

 resembles : the length of the aperture and spire are nearly equal. 



Height 7 lines ; diameter of the last whorl 4 lines. 



Locality. — Ponton. 



Trochus ornatissimtjs, d'Orb. ? var. Pontonis, Morris. 

 Pl. XIV. fig. 10. 



Trochus ornatissimus, d'Orb. Pal. Fr. Terr. Jur. t. 312. f. 6-8. 

 ?T. pileus, Lycett, Ann. N. Hist. 1850, p. 417. 



Testa subconica, umbilicata, anfractibus longitudinaliter costatis, costis (20) 

 subacutis interstitiis transversim striatis, ultimo anfractu carinato, basi 

 planulato vel subconvexo, concentrice semistriato. 



A small but well-marked shell, rather wider than high, formed of 

 few slightly concave volutions, having 15 to 20 acute and prominent 

 longitudinal ridges, the interspaces marked with a few small costulse ; 

 the base flat or but little convex, umbilicated, and the umbilicus sur- 

 rounded by a few concentric striations, which do not extend to the 

 outer margin. 



This species belongs to a small section of the genus Trochus, of 

 which but few allied forms are at present recorded in the Jurassic 

 strata, viz. the T. heliacus, T. lamellosus, and T. Tityrus of d'Orb., 

 and T. pyramidatus, Phillips. Our specimen, which is very imper- 

 fect, agrees with T. ornatissimus, d'Orb., but the base of that species 

 is more convex. 



Localities. — Ponton and Barnack. 



M. d'Orbigny's specimen is from the inferior oolite of Calvados. 



AsTARTE EXCAVATA, Sow. Var. coMPRESSiuscuLA, Morris. 



Compared with the well-known Inferior Oolite shell, this variety 

 presents some marked differences : it is more discoidal, the test more 

 delicate : the fine, irregular, concentric striations but faintly repre- 

 sent the prominent large plications of the typical form : the dimen- 

 sions are at least one-half less ; and the greater number of specimens 

 have still smaller proportions. The young examples of this variety, 

 when only 3 or 4 lines in diameter, are equally distinguishable ; they 

 are very delicate and flattened, with three or four distinct plications 

 near to the umbones, the remainder of the surface being nearly 

 smooth. The ultimate stage of growth in our variety exhibits a 

 greater thickness of test and convexity of form, therein approxima- 

 ting to the type ; and, in fact, but for the inspection of this latter 

 condition, it would be regarded as a distinct species. In the Cottes- 

 wolds and the West of England the type shell occurs in the lower 

 division of the Inferior Oolite : the freestone beds of the middle divi- 

 sion in Gloucestershire contain the variety compressiuscida ; in the 

 upper division of the Inferior Oolite the type reappears : again, in 

 the Great Oolite of Minchinhampton the variety compressiuscida is 

 abundant : the two varieties never occur together. 



Dimensions of the largest specimens: — Height, 13 lines; length, 

 19 lines; diameter throu2;h l)nth the valves, 3 lines. 



