1-JO History nf British Entomostraea. 



reeled backwards, whilst the other three are directed forwards. The 

 first of these three pairs are very short, the second a little longer, 

 whilst the third or last pair are the longest of all, being longer than 

 the anterior pair, though much more slender. This last or poste- 

 rior pair appears to arise from near the junction of the two 

 halves of the body, and may supply, as Muller says, the want of the 

 tail. The mouth is situated in the inferior surface of the anterior 

 half of the body, as in the Cypris, and appears to consist of exactly 

 the same organs as in the insects of that genus, though from their 

 extreme minuteness, and want of lengthened opportunities for exa- 

 mination, I have not been able to make out all the parts. The pal- 

 piferous mandibles, and the first pair of jaws with their branchial 

 plates, are the only parts I have been able clearly to make out, and 

 they resemble in almost every respect the corresponding organs of 

 the Cy prides. The mandible (Plate V. Fig. 21.) is formed of two 

 pieces, the larger of the two, or proper mandible, as in the Cypris, 

 being terminated at the superior extremity by a sharp point, and at 

 the lower or incisive extremity by about six pretty strong teeth, 

 while the other part or palpus consists of three joints plentifully 

 supplied at the extremities of the articulations with numerous se- 

 tae. I failed, however, in making out the small branchial plate 

 which occurs in this organ in the Cypris. The first pair of jaws, 

 (Plate V. Fig. 22.) as in the Cypris, consists also of two parts ; the 

 square plate with the four fingers, (Fig. 22, a.) the superior of which 

 has two joints, whilst the others have only one, and all terminated 

 by a tuft of hairs ; and the branchial plate (Fig. 22, b.) attached, of 

 an elongated oval form, furnished with fourteen long setae, which 

 are given off from both sides. As these organs are so very similar 

 to the corresponding organs in the Cypris, I have no doubt that the 

 other parts (the lips and second pair of jaws) are also the same, and 

 that therefore the supposition of Desmarest with respect to some of 

 the intermediate feet being particular organs is incorrect ; and that, 

 as their use and situation indicate, they are all true feet, and used 

 solely for locomotion ; the posterior or fourth pair perhaps serving 

 in addition one of the uses of the tail, that of cleaning the inside of 

 the shell, for which they are well calculated from their length, and 

 the great degree of mobility they possess. The appendix or short 

 tail is of such an irregular figure, that, until better opportunities oc- 

 cur for examination, I shall not attempt a minute description. The 

 internal anatomy I have not been able to make out at all ; neither 

 have I ever seen any individuals with ova, though this may be ac- 



