190 CERITHIAD.E. 



inner side of the right lip displays more or less evident 

 traces of incipient raised crenre at the commencement of 

 the throat. The nodules are larger in proportion than in 

 the last species, and consequently the interval on the body 

 between the rows of them is less wide ; moreover, they 

 are disposed to become confluent. 



In both species of Aporrhais, the suture is surmounted 

 by an obscure row of very short and scarcely raised small 

 nodulous folds ; these are rather more prominent in the 

 present shell, whose colouring has usually a stronger tinge 

 of rufous or chestnut, a central band of which colour often 

 runs between the nodules of the spiral belt. 



The digitations are only completely formed in the mature 

 examples ; hence, as Swainson justly observes, the young 

 bear a marked resemblance to Cerithia. 



The animal has been often figured and described. One 

 of the fullest descriptions is that given by Dr. Johnston. 

 We offer a fresh figure from a beautiful drawing by Mr. 

 Alder. It is of a general yellowish-white hue, the tenta- 

 cula mingled yellow and scarlet ; the snout and head 

 thickly speckled with scarlet, markings of which colour are 

 more sparingly distributed on the paler body and sides of 

 the foot ; sometimes they are not present. The muzzle is 

 long and cylindrical, emarginated at its extremity; the head 

 is rather broad, and bears on each side a long cylindrical 

 tentacle, swollen at its base, where the eye is placed on a 

 prominent bulging. The mantle is loose, ample, and digi- 

 tated ; it forms a rudimentary siphon in the region of the 

 canal of the shell, but is not extended beyond it ; the foot 

 is oblong, obtusely angulated in front, and scarcely pointed 

 behind ; on its caudal surface it bears a small elliptical 

 horny operculum of three or four concentric layers. Dr. 

 Johnston remarks that the creature " creeps very slowly, 



