2 THE VOYAGE OF H.M.S. CHALLENGER. 



A discussion of the systematic position of tbe genus Scrolls within the order Isopoda 

 will be best postponed until after a more detailed study of the remaining part of the 

 collection. 



With regard to the alleged affinity of Serolis (and of the Isopoda generally) for the 

 extinct Trilobites, insisted upon by Milne-Edwards,^ I have nothing to add to what has 

 already been said ; the examination of the Challenger collection of Serolis has brought to 

 light no facts which tend to show any close resemblances between the two groups. 



I have to thank Mr. E. J. Miers of the British Museum for kindly facilitating my study 

 of the specimens of Serolis preserved in the national collection. 



HISTORICAL NOTICE. 



The first recorded notice of Serolis is contained in Fabricius's Systema Ento- 

 mologiae, which was published in 1775. Under the name of Oniscus 'paradoxus is a 

 short description of a species subsequently named Serolis fabricii by Leach, and which 

 was obtained at the Straits of Magellan during Captain Cook's second voyage. 



A few years later (1767) Fabricius briefly defined this species in his Mantissa 

 Inseetorum ; in both these works Oniscus is placed in the class Synistata, which forms 

 the third class of the four into which Fabricius divided what are known now as Arthro- 

 poda, and which included, besides the Isopoda, the majority of the Insecta now classed 

 within the orders Hymenoj^tera, Diptera, and Heteroptera. 



In his Species Inseetorum, published in 1781, Fabricius gave another description 

 of this species, still under the name of Oniscus i^'^f'^doxus ; here Fabricius hints at the 

 Trilobite affinities of the genus " An protypon Entomolithi paradox! ? In multis 

 certe convenit." 



In 1798 appeared Fabricius's Entomologia Systematica, which is a considerable advance 

 upon his earlier works. His eighth class, Polygonata, includes all the Crustaceans belong- 

 ing to Latreille's order Isopoda as well as the genus Monoculus;^ the name Oniscus 

 paradoxus is altered to Cymothoa paradoxa, and a fuller definition of the genus is given. 



Fabricius's Cymothoa paradoxa was first recognised as the type of a new genus by the 

 English naturalist Dr. W. E. Leach ; in the twelfth volume of the Dictionnaire des 

 Sciences Naturelles, published in the year 1818, is an article by Leach on the Cymothoadae, 

 where CymotJioa paradoxa is redescribed under the name of Serolis fabricii. 



In 1825 Desmarest in his Considerations generales sur les Crustaces recapitulated 

 Leach's description of Serolis fabricii. Both Desmarest and Leach denied the supposed 

 affinities of Serolis with the Trilobites. 



' In 1833 James Eights described in the Transactions of the Albany Institute, vol. ii. 



' Arch. d. Mus., t ii. p. 5 ; Ann. d. Sci. Nat., ser. 6, t. xiL art. No. 3. 

 ^ Monoculus includes aE tlie members of the order Entomostraca. 



