Mr. W. Clark on the Skeneadse. 45 



Lower surface of the animal, without the shell, magnified 25- 

 35 times. 



# Explanation. 

 a. Genitale. 

 ^ b. Semi-serrated neck-lobe. 

 c c, c. Curved auricles of the 

 e. Shorter plain neck-lobe. 

 d. Anus. 



The other organs shown are the eyes and ciliated tentacula. 

 The vibracula, springing from tubercles of the operculigerous 

 lobe, which carries an orbicular spiral corneous operculum of 

 6-8 gyrations, and the sole of the foot. 



Trochus seijmloides, Mont, (certe). 

 Skenea divisa, Fleming et auct. 

 Animal inhabiting a discoid white shell of three spiral turns, 

 striated around the umbilicus of the body- volution with fine 

 capillary lines, the upper part of the whorl being plain ; it is 

 pure hyaline white, except the eyes and head-disk. The head is 

 a rather long, broad, finely wrinkled proboscidal muzzle, with a 

 vertical fissure, having a pale red or pink disk, from whence the 

 corneous jaws and lingual riband may sometimes be seen in ac- 

 tion, but not so conspicuously as in the Rissoce \ the tentacula 

 are long, flattish, frosted on the central line of the stamens, not 

 irregularly setose at the edges, but most elegantly clothed, each 

 on both sides, with 12-14 long hyaline cilia, arranged in sym- 

 metrical series, inclining obliquely from base to point, and dimi- 

 nishing in length in like manner. I have never seen tentacula 

 so elaborately adorned : the eyes are very large, black, and lateral, 

 attached nearly at the external bases on round inflations to the 

 main stems, there being no distinct pedicles : no head-lobes were 

 detected. There are two neck-lappets of different form, the one 

 on the right side being narrowish, flat and semiserrated ; that of 

 the columellar range is shorter, more suboval, and plain. The 

 foot is subtruncate or subrotund in front, superficially labiated, 

 forming at the angles long curved linear auricles somewhat of 

 the shape of the Murex varicosus (Nassa, nonnull.), but longer 

 in proportion, thin at the edges of the sole, which is not fringed ; 

 it is moderately long and rather obtusely pointed ; the operculi- 

 gerous lobe is also plain, the prototype of the sole, though dimi- 

 nished to be well within its margins ; it carries near the extre- 

 mity the circular corneous moderately close-set spiral operculum 

 of 6-8 turns, and on each side, at equal distances, three not very 



