348 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.39. 



He also mistook a young female without egg-strings for a male, as 

 he had done in several other instances. 

 Claus, in speaking of the Ergasilidse, says: 



Thersites mochte demnach generisch mit Ergasilus zusammenfallen, zumal auch 

 die Gestaltung der Mundwerkzeuge keine wesentlichen Abweichungen zu bieten 

 scheint und die colossale Auftreibung des Weibechens dem Kopf und ersten Brust- 

 eegment angehort (1875, p. 339). 



On the next page he states that Pagenstecher mistook the mandi- 

 bles for the first maxillipeds, but he gives us no description of the 

 mouth-parts as they should be, except the above statement that they 

 correspond to those of Ergasilus. 



Canu, in his excellent work Les Copepodes du Boulonnais (1892), 

 published a short account of the mouth-parts of Thersites gasterostei. 

 He found a pair of falciform mandibles, a rudimentary maxilla, re- 

 duced to a mere stump, carrying two slender setae, as in all the genera 

 of the Ergasilidse, and what he called the second maxilla, posterior 

 to the previous pair and corresponding to the second maxillae in 

 Ergasilus and Bomolochus. This is really the first description of 

 the mouth-parts that can be looked upon as at all accurate, and it 

 is unfortunate that it was so well concealed in Canu's systematic 

 treatise. 



T. Scott in one of his memoirs (1900) mentions this description by 

 Canu under the synonymy of Thersites, and then gives us another 

 excellent description of the female, accompanied by admirable figures. 

 He finds four pairs of mouth-parts, a pair of mandibles with a bilobed 

 and pectinate cutting blade, rudimentary maxillae, simple "first 

 maxillipeds," and three-jointed "second maxillipeds." These last 

 consist of an enlarged basal joint and a curved terminal two-jointed 

 arm, tipped with four or five strong apical spines. He also gives us 

 the details with reference to the swimming legs. 



In the following year (1901) we find Gadd trying to establish a 

 new species, which he calls Ergasilus liuncinatus, as distinct from the 

 gasterosteus of Pagenstecher and Kroyer. But his specific distinctions 

 are based upon comparisons with the imperfect descriptions of the 

 two authors just mentioned. He was evidently unacquainted with 

 the more accurate descriptions of Canu and Scott, for he does not 

 even mention them. While his distinctions seem fairly valid, there 

 are two facts which greatly weaken his claim. 



First, he entirely overlooked the first maxillae, not only in this "new 

 species," but also in another species of Ergasilus, which he presents 

 in the same paper. If he had found these maxillae, it would have 

 radically changed his interpretation of the mouth-parts. Again, the 

 figure he has given us of the mouth-parts oV^hiuncinatus^' is inverted, 

 the "first maxilliped" being represented as superior (or anterior) to 

 the "maxilla" (which latter is really the mandible). 



