368 M. T. Thorell on the Systematic Position of the Argulidse. 



finer texture, approaching that of the lower wings. The claws 

 of the tarsi are strong, powerful, and well adapted for clinging. 



In this animal we seem to have a combination of two plans of 

 adhesion : there are the claws and claspers and flaps for hold- 

 ing on by ; there is the hollow underside for adhering by ex- 

 hausting the air between it and the stone it clings to, on the 

 principle of the air-pump. If, when it settles on the stone and 

 adjusts itself, its tracheae are full of air, and it then expels 

 the air and by muscular power draws in the skin of the abdomen 

 and underside generally, it must, of course, leave a vacuum, 

 and consequently adhere like a sucker. 



This species from the mountains of Brazil is the only one of 

 whose aquatic habits any account has been received; but the 

 genus, although individuals are rare (as with most species which 

 only show themselves at night), is widely distributed. 



The following are the species known up to the present time, 

 with their localities, taken from Westwood's recent Monograph 

 of the Phasmidse : — 



Prisopus flabelliformis, Stoll. Brazil ; Cayenne. 



— — spiniceps, Burm. Do. do. 



Ohrtmanni, Licht. East Indies. 



horridus, Westw. Columbia. 



Horstokkii, De Haan. Cape of Good Hope. 



» berosus, Westw. Panama. 



phacellus, Westw. Brazil; Ega. 



incertus, Westw. Samarang ; Java. 



cornutiis, G. R. Gray. India. 



cepus, Westw. Bolivia. 



Guerini, Westw. He Maurice. 



Now that their habits are made known, we may expect that 

 specimens will become less rare, and that we shall receive more 

 information regarding their economy and mode of life. 



XXXV. — On Two European Argulidse, with Remarks on the 

 Morphologrj of the Argulidse and their Systematic Position^ to- 

 gether with a Review of the Species of the Family at present 

 known. By T. Thorell. 



[Continued from p. 169.] 



III. 



As the question of the position which the family Argulidse 

 should occupy in the system of the Crustacea is far from having 

 received a satisfactory solution, it will not be out of place here 

 to dwell somewhat further on this subject. Referred by Linne 



