244 BRITISH ENTOMOSTRACA. 



LinnsBUS, in the tenth edition of his ' Systema Natm-se,' 

 1758, and again in his ' Fanna Snecica,' 2d edit. 1761. 

 notices the Arguhis under the name of MonoculusfoUaceiis, 

 In the 1 2th edition of the ' Systema/ 1767, he unfor- 

 tunately, however, confoimds it with the Cahgus, under the 

 name of Monocidus piscinm. Under this name he refers 

 to the Argulus, as described by himself, in his two last- 

 mentioned Avorks, and by Loefling ; to the Caligus, as 

 described by Baster, in his ' Opuscula Subseciva ;' and to 

 the Prosopistoma, figured by Geofiroy, in his ' Insectes de 

 Paris.' Fabricius, in his ' vSystema EntomologiaB,' 1775, 

 and Gmelin, in the 13th edition of the ' Systema Natura?,' 

 repeat this error, giving the species Monocidus pischms, 

 with all the faulty synonyma. Geoffroy, in his ' Insectes 

 de Paris,' 1762, observing that this, and some other 

 species of Entomostraca, had two eyes, formed the genus 

 Binoculus to receive them. This little parasite he had 

 once fonnd upon the stickleback ; but not having time to 

 examine it attentively, he has given no lengthened de- 

 scription, merely noticing it under the name of Binoculus 

 ^asterostei."* 



Ledermiiller, in his ' Amusements microscopiques,' 

 part i, 1764, has given a figure of the Argulus, and de- 

 scribes it as " a small aquatic insect," which he thought 

 worthy of attentive consideration. His figure is enor- 

 mously magnified, and very indifferent. Miiller is the 

 first author wdio has given it the name of Argulus. In 

 his 'Entomostraca,^ 1785, he established the genus 

 Argulus, and described two species, indicating, besides, a 

 third. The last is a very doubtfid species, while the two 

 first are the same, the only difference being in age, 

 Miiller erroneously considering the young animal as dis- 

 tinct from the adult. 



* The second species of Lis genus Binoculus be calls Binoculus luemi- 

 sphccricua, and gives as synonyms the references of Frisch, Loefling, and 

 LinnjEus (lOtli edit.), to the genus Argulus. An examination of the figure 

 accompanying the description distinctly shows, however, that tliis is a totally 

 different animal, being the Prosopistoma of Latreille. 



