Mr. A. Hancock on the Anatomy 0/ Antiopa Spinolse. 27 



ness, of a peculiar boruy texture^ apparently porous within, 

 admitting readily the point of a needle ; their form is subtrian- 

 gular when seen in front, each having attached to the anterior 

 angle a plate or cap {a), which is provided with two parallel 

 cutting edges, the outer one (6) being denticulated, the inner (c) 

 smooth. The denticulations are about twelve in number, very 

 large, compressed and lancet -formed, with their points tipped 

 abruptly with black : theii* bases being pale have not a httle 

 the appearance of fonning a second row of teeth. This appear- 

 ance probably deceived M. Blanchard, who describes two denti- 

 culated plates. The inner edge is quite smooth, and separated 

 from the outer one by a deep groove : the function of this edge 

 is rather problematical. The jaws are strongly articulated above 

 in front, at a point (fig. 5 d) which is furnished with a projecting 

 process or fulcrum. 



The tongue is large, and stands up from the floor of the buccal 

 cavity in front of the oesophagus ; it is formed as in Doris, being 

 tubular behind (PI. II. fig. 6, and PI. III. fig. 2 b), with the 

 frontal portion (a) turned over, as it were expanded like the 

 mouth of a trumpet. This is the only portion of the organ that 

 can act as a prehensile instrument, the spines being exposed and 

 turned with their points towards the gullet. The spines behind 

 line the tubular portion, and are covered by a soft, delicate mem- 

 brane. Here they are genei-ated, and retained until gradually 

 pushed forward to make up the deficiency occasioned by the loss 

 of those in front. 



The spines are firmly attached to a stifGsh membrane, which 

 rests upon a muscular support capable of moving backwards and 

 forwards, and of giving to them the necessary prehensile action. 

 When the tongue is removed from this muscular support and 

 spread out, it (PI. II. fig. 7) is found to be about twice as long 

 as it is broad, slightly narrowed behind (a), and a little rounded 

 at both extremities, with the whole surface covered with trans- 

 verse rows of plain, stout, recurved spines (figs. 8 & 9) of a deep 

 amber colour, giving to the rows when seen with a low magnify- 

 ing power a dark purple-brown hue. There are thirty of these 

 rows, each containing eighty spines, one spine being central 

 (fig. 8 a), of the same size, plain and recurved like the rest. 

 From this the lateral portions of the rows, on either side, slope 

 forward, gi\ing to the tongue a bipaitite appearance. 



The oesophagus (Pis. II. & III. fig. 1 b) is rather wide, very 

 short and internally plicated; it passes from about the middle 

 of the upper aspect of the buccal mass, and opens into the lower 

 portion of the stomach in front. This latter organ (c) is placed 

 far forward in the visceral cavity, a little on the left side. It is 

 transversely elongated, of considerable size, exhibiting through its 



