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XII. Notes on the genus Prosopistoma of Latreille. By 

 J. O. Westavood, M.A., F.L.S., Pres. Ent. 

 Soc, &c. 



[Read 4th April, 1877.] 



Geoffroy, the historian of the insects of the environs 

 of Paris (v. 2, 17, p. 660, pi. 21, fig. 3), first made us 

 acquainted with a small aquatic insect, under the name of 

 " Le Binocle a queue en plumet," which he placed amongst 

 the Apterous genera, and which subsequently received the 

 names of Binoculiis peruiigerus, Latreille, and Binocle 

 jiisciforme, Dumeril. The insect must evidently be of 

 great rarity, as no Entomologist appears, luitil recently, 

 to have met with it except its original describer, and its 

 minute organization was not sufficiently described to allow 

 of all its relations being discovered. In the same genus 

 Binocle, Geoffroy introduced al^o the Apus caneriformis 

 and the Argulus foliaceus. 



In 1833 Latreille, hoAvever, recalled attention to this 

 almost unknown animal in a memoir which he published 

 in the " Nouvelles Annales du Museum d'Histoire 

 Naturelle," t. ii. p. 23, entitled "Description d'un nouveau 

 genre de Crustaces," established on an insect which he had 

 found in a box of Madagascar Coleoptera, having much 

 the appearance of a Gyrinus, and which he did not 

 hesitate to regard as congeneric with Geoffi'oy's Binoculus. 

 The Madagascar specimens were unfortunately in a more 

 or less mutilated condition ; and after a comparison of their 

 structure (with such details as had been given by Geoffi'oy), 

 and that of such genera as Apus, Limulus, &c., Latreille 

 came to the conclusion that the insects in question could 

 not be arranged with any known Entomostracous or 

 Branchiopodous group, and that, "de tons les Ento- 

 mostraccs ou Bianchiopodes, la coupe qui doit les com- 

 prendre est, par la composition de la tcte, offrant deux 

 antennes, deux yeux a rescau, quatre appendices maxil- 

 laires, representant les mandibules et les machoires et une 

 lame mcntonniere, ainsi que par le nombre et la forme des 

 pattes, la plus rapprochec des insectes ]n'oprement dits." 

 Although the ^Madagascar specimens exhibited no terminal 



TRANS. ENT. SOC. 1877. — PART III. (OCT.") 



