248 BRITISH ENTOMOSTRACA. 



the animal to fix itself to its prey. Ledermiiller describes 

 them as antenuse, and since his time, Dana and Herrick, 

 and M. Edwards, have shown them to be the trne antennae 

 of the animal ; while, according to the latter author, the 

 posterior pair of organs are the lirst pair of foot-jaws. 



The organs of the mouth are of a complex nature. The 

 most prominent part is a long, sharp-pointed siphonal 

 tube (t. XXXI, f. d, c). It arises at a considerable distance 

 behind the antennae, and is formed of a very fine tube, in- 

 closed in a flexible sheath, llie extremity terminates in 

 a very sharp point, at the top of which we see the orifice 

 of a canal, hollowed out of the interior, which is prolonged 

 to the commencement of the oesophagus. It is moveable, 

 the animal being able to thrust it out rapidly from its 

 sheath, carry it right or left, and project it far enough to 

 reach the anterior edge of its shell. It can also cause it 

 to enter into its sheath with the same rapidity by means 

 of a slender nuiscle, which at one part is attached to the 

 base of the sheath, and at the other to the middle of the 

 trunk. The sheath is nothing but a prolongation of the lip, 

 while the sharp-pointed portion constitutes the analogue 

 of the mandible. Below the insertion of this siphon we 

 see a convex, oval mass (f. d), containing the rest of the 

 apparatus of the mouth. According to Dana and Herrick, 

 who have described this part with great care, these con- 

 sist of what is perhaps the inferior lip, and two pairs of 

 maxillae in a rudimentary state. These authors consider 

 that Jurine, who describes the convex, oval mass men- 

 tioned above as the heart, is quite mistaken ; and that the 

 motion which he considered the palpitation of the heart, 

 is nothing but the rapid motion of the maxillae. 



The feet of the Ai-gulus are generally described as of two 

 different kinds : one used either for walking Avith or 

 fixing itself upon its prey ; the other adapted for swimming 

 when the animal is at large. What have been called the 

 ambulatory legs are two pairs in number. They are the 

 second and third pairs of foot-jaws. The anterior pair, or 

 second paii- of foot-jaws, (t. XXXl, f. e,f) is of a very 



