ORDER PCECILOPODA. 359 



the largest. Their body has no tail, and the testa forms only 

 a plate, covering the anterior portion of the body. Their other 

 organs are developed by degrees, in the course of successive 

 moultings. M. Valenciennes, employed in the Museum of 

 Natural History, has remarked that these animals were often 

 devoured by the bird known vulgarly under the name of wag- 

 tail. 



The known species being by no means numerous, it is not 

 necessary to form, as Dr. Leach has done, with those which 

 have a lamina between the filaments of the tail, a genus proper 

 (Lepidurus). '^nch \& \\ieMonoculusapus,ljmn.; SchoefF. 

 Monoc. vi. ; Limule serricaude, Herm. fils. ; Desm. Consid. 

 lii. 2. The keel of the buckler is terminated posteriorly in 

 a small spine, which is not seen in the following, Apus 

 canciformis {Binocle a queue en Jilet, Geoff. Insect, xxi. 4 ; 

 Limulus palusiris, Mlill. ; SchoefF. Monoc. i. — v.; VApus vert. 

 Bosc. ; Desm. ibid, li. 1.) ; the latter has no lamina between 

 the filaments of the tail. It is the type of the genus apus 

 proper of Dr. Leach. He has figured another species, Apus 

 Montagui, Edin. Encyc. Suppl. i. — xx. 



THE SECOND ORDER OF ENTOMOSTRACA, OR 

 THE SEVENTH AND LAST OF THE CLASS 

 CRUSTACEA. 



PCECILOPODA 



Is distinguished from the preceding by the diversity of form 

 in the feet, the anterior of which, of an indeterminate num- 



