12 Foord and Crick — On Prolecanites compressus. 



largei' than the figure. It is somewhat elliptical, its diameters being 

 172 mm. and 142 mm. respectively. It was obtained from the 

 Carboniferous Limestone of Little Island, Queenstown Harbour, 

 opposite Blackrock, the locality which yielded Sowerby's types. 



The sides of the whorls, especially in the septate portion of the 

 shell, are flattened, feebly convex, their greatest convexity being at 

 about the middle of the lateral area ; the sides of the body-chamber 

 are slightly inflated. In the outer whorl the portion of the lateral 

 area adjoining the periphery becomes somewhat concave. The 

 periphery is flattened, and bounded on either side by a subangular 

 edge ; at the commencement of the outer whorl the periphery is 

 rather convex in the centre and somewhat concave between the 

 centre and the subangular border. As the shell increases in size 

 the peripheral area becomes more flattened, and its edges more 

 prominent (see Fig. 4), so that the concavity of the portion of 

 the lateral area adjoining the periphery becomes more pro- 

 nounced. Eather more than three and a half whorls can be 

 counted, but the central portion of the fossil — i.e. up to the point 

 where the diameters of the shell were 11 mm. and 9 mm. respectively 

 — is wanting. The inner area of the whorl is well defined, and 

 slopes towards the umbilicus; this slope has probably been increased 

 by the distortion which the specimen has suffered owing to the 

 cleavage of the rocks in which it was imbedded. The slope is 

 apparent, though less distinctly marked on the body-chamber, and 

 where the shell is absent this inner area is scarcely defined on the 

 cast. 



The latter half of the outer whorl is occupied by the body-chamber ; 

 it bears only fragments of the shell. One side of the septate portion 

 of the specimen is covered by the test. This exhibits an almost 

 perfectly smooth surface; there are no traces of longitudinal lines on 

 any of the inner whorls. On the last part of the septate portion, 

 that is, on the first half of the outer whorl, there are, however, very 

 faint indications of fine transverse curved lines sweeping forward 

 near the periphery. A constriction near the commencement of the 

 last whorl follows the course of these transverse lines, and doubtless 

 indicates the form of a previous aperture. The form of the con- 

 striction cannot be clearly made out on the periphery. The other 

 side of the last half whorl of the septate portion is denuded of the 

 test, so that the septa are shown very distinctly. 



Some fragments of the test remaining on the body-chamber are 

 very well preserved. They show that on the lateral area of the 

 body-chamber the test was nearly smooth, marked only with fine, 

 subregular, faintly-incised lines about one millimetre apart (see 

 Fig. 3), which extend in an almost radial direction over the middle 

 portion of the side of the whorl and sweep forward as they approach 

 the periphery, meeting the margin of the latter at an angle of about 

 50°, and forming on the subangular margin prominent imbricating 

 lines. These fine lines cross the inner area of the portion of the 

 whorl forming the body-chamber in a rather shallow curve, concave 

 forwards. 



