TANAIDACEA AND ISOPODA— TATTERSALL. 251 



suivants, surtout de ceux de la septieme paire, la reduction de la partie pleale, sembleut 

 bien indiquer, a defaut d'autres renseignements ethologiques, que nous sommes en 

 presence d'un type degrade par la vie parasitaire et qui, sans doute, aura ete detache de 

 son liote au moment de sa capture. L'absence d'organes et de produits genitaux font 

 penser a une forme jeune, mais d'autre part la regression de certains appendices, comme 

 la spe'cialisation si caracterise'e de certains autres, moutre bien que c'est un type sinon 

 adulte, du moins deja parfaitement adapte a un genre de vie bien particulier. 



" Je designerai cet Isopode sous le nom de Rhabdocheirus incertus pour rappeler et 

 la conformation caracteristique des cinq dernieres paires de pereiopodes et I'incertitude 

 on nous sommes de son o-enre de vie." 



My examination of this species on the whole confirms Bonnier's description. The 

 only point in which I differ from him is in the interpretation of the antennules 

 and antennae. The single-jointed appendages which Bonnier calls the antennae, I 

 should interpret as the antennules. The head appears to me to be folded downwards 

 and backwards, and this curious bending of the head has led to the antennules 

 appearing on the ventral surface of the head and actually behind the antennae. It 

 follows, therefore, that the appendages called antennules by Bonnier, I believe to be the 

 antennae. 



The figures (pi. XI, figs. 4-13) which I give herewith of the appendages show 

 their essential structure in detail, and bear out Bonnier's account. They show specially 

 the sub-cheliform appearance of the dactylus of the fourth to seventh thoracic limbs 

 and the curious form of the last pair of appendages. 



The animals are, I think, almost certainly immature, and will probably prove to be 

 young specimens of one of the Epicaridea parasitic on some of the Pelagic Decapoda 

 or Mysidacea. If so, however, the adult must probably belong to a type of Epicaridea 

 hitherto undiscovered, for Rhabdocheirus differs widely from any young stage of 

 Epicaridea yet known. 



