508 Geological Society. 



and Natica clausa are found living in the Arctic ocean, but the two 

 species of Nassa and the Fusus are unknown in a recent state*. 



Between three and four miles north of Ramsey, the beds of this 

 deposit occasionally exhibit a very remarkable concretionary struc- 

 ture. The sand has here been cemented into masses, which are ex- 

 tremely hard, and even sonorous when struck, though the sand in 

 which they are imbedded is perfectly loose. The cementing ingre- 

 dient, which the application of acid proves to be carbonate of lime, 

 seems to have been influenced in its operations partly by the planes 

 of stratification, and partly by the direction in which the sand has 



* Mr. Strickland gives the following characters of three species of shells 

 found in the newer pliocene beds of the Isle of Man ; specimens of which 

 have been examined by several eminent conchologists in London, who all 

 concur in believing them to belong to extinct species. 



u 1. Nassa monensis, Forbes, in Mem. Wern. Soc, vol. viii. p. 62. Small; 

 volutions about six, rounded ; suture deep ; ribs, nine on the first volution, 

 straight, rather distant, strong, subacute, and slightly oblique. The first 

 volution has thirteen, and the second six, distinct, regular, thread-like, spiral 

 striae, crossing alike the ribs and their interstices. Aperture orbicular-ovate, 

 canal very short and oblique, pillar-lip simple, outer lip with about five 

 slight marginal denticles on the inside, and an external rib slightly more 

 developed than the ordinary ribs. Total length, 7 lines ; first volution, 

 3| lines ; breadth, 4£ lines ; angle of spire, 40°. 



" Obs. Resembles the recent N. macula, but is larger, more ventricose, has 

 fewer ribs, and the terminal rib is less suddenly developed. 



"2. Nassa pliocena, Strickland, 1843. Large; volutions about seven, 

 rather flat, with a distinct thread-like suture ; ribs, twelve on the first volu- 

 tion, straight, distant, rounded, very slightly oblique ; the interstices flat, 

 exceeding the width of the ribs by one-half. The first volution with thir- 

 teen, and the second with about nine fine spiral striae, only visible in the in- 

 terstices, the ribs being smooth ; but this may be due to attrition. Aperture 

 ovate ; canal very short and oblique ; pillar-lip with about five obscure den- 

 ticles, and a spiral groove immediately behind the canal, continued into the 

 interior of the shell. Outer lip with about eight internal marginal denticles ; 

 no rib at the back. Total length, 1 inch 8 lines ; first volution, 8 lines ; 

 breadth, 9 lines ; angle of spire, 40°. 



"3. Fusus Forbesi, Strickland, 1843. Fusus nov. sp. Forbes, Malacologia 

 Monensis, pi. 3. f. 1. Middle-sized; volutions about six, slightly rounded, 

 suture distinct; ribs, eleven on first volution, straight, rounded, smooth 

 (perhaps from attrition); interstices concave, and hardly wider than the 

 ribs. First volution with about fifteen, and second with about seven distinct, 

 rather irregular spiral stria?, of which those on the first volution are alter- 

 nately large and small. They are only visible in the interstices of the ribs. 

 Aperture ovate, double the length of the canal, which is straight, and rather 

 oblique to the left. Pillar-lip smooth, with one obscure denticle at the pos- 

 terior end. Outer lip with about ten small linear denticles within, conti- 

 nued a short way into the mouth, and a well-marked external rib remote 

 from the margin. Total length, 1 inch 3 lines ; first volution, 7 lines ; 

 breadth, 8 lines ; angle of spire, 43°. 



" Obs. This species belongs to a group of Fusus which seems closely allied 

 to Nassa. First described by Mr. E. Forbes, from a worn specimen found 

 on the coast of the Isle of Man, and supposed by him to be an existing spe- 

 cies, but the discovery of additional specimens in situ proves it to be a 

 genuine fossil." 



