FISSURELLID.E. 255 



(J. G. J.) ; Mull and Skye, 30-90 f. (Forbes, M^An- 

 drew, and Barlee) ; Moray Firth (Dawson) ; Shetland, 

 75-80 f. (Barlee and J. G. J.) . It has not yet been 

 noticed as fossil; and the only foreign locality is the 

 coast of Sweden, at a depth of only 12 f., with Mytilus 

 Adriaticus and Branchiostoma lanceolatum (^lalm) . 



The animal is active for its size. Forbes and Hanley 

 remarked that the tongue is very long, and the brown 

 central spines conspicuous under the microscope, re- 

 sembling bramble- thorns in miniature. 



It was named by the late Mr. W. Thompson ''Patella'^ 

 exigua, Forbes.'^ 



Family II. FISSURE'LLIDiE, (Fissurelladce) 

 Fleming. 



Body conical or semioval : mantle folded in front, so as to 

 form a tubular process, which occupies a slit in the margin or 

 near the summit at that end of the shell or else a hole in the 

 crown : head prominent, with a short muzzle, furnished (as in 

 the Patellidie) with jaws and a spinous tongue, which latter is 

 shorter than in that family and scarcely convoluted : tentacles 

 spike-shaped : eyes seated on short tubercles, one at the outer 

 base of each tentacle : gills forming two symmetrical and 

 somewhat triangular plumes, one on each side of the neck : 

 foot thick, studded at the upper side or covered entirely with 

 papillae : vent anterior, placed in the middle between the gill- 

 plumes. 



Shell cap-shaped or ovately conical, with a sHt in front or 

 near the cro^^n on that side, or else a hole in the centre ; it is 

 ribbed lengthwise and often cancellated by concentric or trans- 

 verse striae : beak turned towards the hinder part, where it 

 forms a short and complete excentric spire, always in the young 

 and mostly in the adult : mouth extremely wide and occupying 

 the entire base. 



The fissure or perforation of the shell indicates a cor- 

 responding formation of the animal, a fact which to this 



