94 



MR. C. EOUSFIELD OX THE 



Fabricius the description of a worm whicli he described as Nais 

 •quodricuspida, which appears to have some affinity with the genus 

 Dero. Apparently this species has not since been observed, 

 though from the description given by Fabricius (10) it seems 

 sufficiently well marked *. 



G-ervais (11) reclassified the Naididae, and renamed the genus 

 Dero ; Urondis being the designation applied to it, apparently 

 from the peculiarity of the tail. He appears to have been the 

 first to remark tliat Miiller's figures evidently represented two 

 distinct species. In Common with some other writers, he 

 included the Nais barhata of MiiUer, in spite of the fact that the 

 latter is described as having a simple truncated tail. 



GErsted (19) gave only a very short account of the genus, 

 calling it JProto (Oken). 



Grrube (12), whilst contributing little or nothing to our know- 

 ledge of the genus, made some interesting remarks on its syste- 

 matic position, and referred to two marine forms, described by 

 Dujardin (8) and Duges (7) respectively, which he regarded as 

 allied to Dero. Having carefully compared the papers referred 

 to by Grube, I am unable to agree with his conclusion. Grube 

 also remarked on the confusion in the nomenclature, professing 

 himself unable to decide the question of the origin of the name 

 Protof. It should be remarked that Grube does not mention 

 having seen Dero. 



Bosc (4) mentioned, under the name of JV^ais auricularis, a worm 

 found in Carolina with, a tail formed by a large tubercle, in the 

 middle of which is the anus, — a description which would well 

 apply to a Dero in a contracted state. 



Pennant (21), Shaw (27), Stewart (28), and Turton (30) gave 

 descriptions of Nais digitata which afi'ord no assistance in iden- 

 tifying the form ; and the same may be said of a long paper by 

 Houghton (13), who, having found the genus in England, instead 



* " Nais verrucis lateralibus bifidis setosis cirris abdominal ibus et cauda 

 quadrifida." 



t The origin of this name remains unknown. CErsted attributed it to Oken, 

 in whose work no trace of it is to be found ; nor is it likely that he would have 

 given to one genus two different names. Another writer, in spite of Grube's 

 remark, attributed the name to him. The only feasible explanation appears 

 to be that some unknown writer, between the time of Gervais and CErsted 

 {%. e. 18o8 and 1843), originated it in a paper which has been lost. The ' Nomen- 

 clator Zoologieus' of Agassiz gives both names, and attributes both to Oken, but 

 evidently wrongly. The etymology is there given as ^tpw, cufem exuo. 



