Prosopistoma of I^atrcille. 191 



doutes sur la vraie nature clu pretenclu Cnistace de Geof- 

 frey, de Dumeril, et de Latreille, tous ces doutes seraient 

 dissipes a la fois par la seule presence des tracliees qu'on 

 observe cliez lui. Or, des dissections minutieuses et que 

 nous croyons exemptes d'erreur, nous ont appris qu'il 

 existe sous la carapace, a la partie laterale des cinq pre- 

 miers segments abdominaux de notre animal, cinq paires 

 de fausses branchies tres-analogues a celles de plusieurs 

 larves d'Ephemerines, et notamment du genre Casuis." 

 An elaborate plate of details accompanies this memoir, 

 from wliicli the figures in Plate V. are copied, and which 

 are here introduced in order to allow comparison with them 

 of the various details observed by myself in examining 

 Latreille's existing types of his Madagascar species, which 

 I had the pleasure to find and obtain, in one of my visits 

 to Paris, in the Avreck of his collection of the miimte 

 Crustacea and other Linnean apterous insects. 



M. E. Joly has published several other papers on the 

 insect of Geoffi-oy, in the Memoires de la Societe des 

 Sciences Naturelles de Cherbourg, 1871, t. xvi. ; also, 

 " Nouvelles recherches tendant a etablir que le pretendu 

 Crustace, decrit par Latreille sous le nom de Prosopis- 

 toma, est un veritable insecte de la tribu des Epheme- 

 rines," published in the Revue des Sciences Naturelles 

 (of Montpellier), tome iv. Juin, 1875;* also an article 

 " Sur le Prosopistoma," in the Feuille des Jeunes Natu- 

 ralistes, ler Mars, 1876, Sixieme Annee, No. %6\ and 

 " Notes sur les caracteres d'un larve d'insectes de la 

 famille des Ephemei'ines" (Rev. Soc. Sav. (2)iii.). This 

 larva, found near Toulouse, possesses respiratory organs 

 protected by tAvo trapezoidal lamella, and is doubtingly 

 referred to the genus Ccenis. 



The figures o^ Prosojnstoma jmnctifrons and its details, 

 which jNI. E. Joly has given in the Annales des Sciences 

 Naturelles (5 Scr. Zool., tom. XAa. pi. 13), disagree in many 

 important particulars fi.'om the examination which I have 

 been able to make of a specimen of that species sent by 

 M. Joly himself to Mr. MacLachlan, and which I find 



* In this memoir, Messrs. Joly have endeavoured to prove the correct- 

 ness of their opinion as to the Ephemcrideous nature of these creatures, by 

 the discovery of the sinjrular New Zealand I'4)hemcrideons Oniscuja.ftcr 

 Wnkcficldi of MacLachlan (II. Linn. Soc. xii. p. 145), and the pupa of 

 Bactlsca obesa of Say, figured and described by Walsh. 



