NO. 1788. NORTH AMERICAN ERGASILID^— WILSON. 279 



From this list it can be seen that each mouth-part has borne at 

 least three different names, while the first maxillse in the genus 

 Ergasilus, and in many species of the genus Bomolochus have been 

 overlooked by every author except Claus and Gadd. Both of these 

 investigators describe the same species, Ergasilus sieholdii, but give 

 very different names to the mouth parts, as can be seen. 



Such being the conditions it remains to determine the correct 

 names for the various appendages, and to state the reasons for the 

 decisions made. 



The mandibles. — Most of the authors are agreed that the first pair 

 should be called mandibles. Heller designates them thus in his 

 Bomolochus (Irodes) gracilis, but calls the same organs in B. tnegaceros 

 first maxillipeds. In the latter case he claims to have found the 

 mandibles entirely inside of the mouth. If this be true it is the only 

 instance in the entire family, and would at least be worthy of a 

 generic distinction. This, and the fact that Heller wholly over- 

 looked the first maxillae, while he contends that the maxillipeds 

 correspond to the first maxillae in Caligus and Lepeophtheirus, enable 

 us to dismiss his objection as a case of mistaken identity. (See p. 384.) 



Wright (1882) and Fellows (1888) call the first pair of appendages 

 mandibles, but the palps attached to them they call maxillae. This is 

 easily explained from the fact that neither of them found the true 

 maxillae, and hence they were forced to substitute something for 

 them. 



Gadd (1904) describes and figures the mouth-parts of Ergasilus 

 sieholdii and claims that the first pair of appendages are maxillae, and 

 that the true maxillae are their palps. 



As reasons for his belief, he declares (a) that the latter are attached 

 to the former in the manner of palps; (b) that some forms like the 

 genus Lichomolgus (which he includes in the Ergasilidae) possess a 

 rudimentary sucking mouth with inclosed mandibles. Hence if there 

 were any mandibles in Ergasilus they would be inside the mouth, 

 where Heller claimed to have found them for Bomolochus. And the 

 fact that there are none there means that they have degenerated 

 enough to have disappeared. This sounds plausible, but any assur- 

 ances the text may have given us are quickly dispelled when we come 

 to examine Gadd's figures. 



After all an author's illustrations give us the best idea of what he 

 has really seen ; the text may contain much that is imaginary in the 

 way of interpretation. 



Gadd figures the mouth-parts of two species which he refers to the 

 genus Ergasilus. The first, which he calls E. hiuncinatus, appar- 

 ently belongs to the genus Thersitina, but however that may be, he 

 has figured the mouth-parts upside down (pi. 1, fig. 19). That is to 

 say, the "maxilliped" is placed above (in front of) the ''maxilla" on 



