NO. 1788. NORTH AMERICAN ERGASILID.^—WTLSON. 385 



true maxillipeds was to call them "seitlichen Hornhaken." But it 

 would be manifestly impossible to have two species belonging to the 

 same genus in one of which the mandibles were inclosed within 

 the mouth-tube while in the other they were entirely free. 



What Heller really saw inside the mouth can not even be surmised, 

 but at all events it was not a pair of mandibles, for these are in their 

 normal position at the side of the mouth. 



Again Heller did not see the first maxillae in any species of Ergasilus 

 or Bomolochus which he described ; they do not appear in his figures 

 and are not mentioned in his text. If he had seen them he would 

 never have placed one pair of ''maxillipeds" in front of them. But 

 his most serious error is the assumption that the prehensile hook 

 in gracilis corresponds to the maxilliped in megaceros, when the two 

 are entirely different in structure and position. The hook in gracilis 

 corresponds to that found in Caligus and Lepeo'pliiheirus in structure, 

 function, and sex variation. But if so, the species gracilis can not 

 belong to the genus Bomolochus, but must be made the type of a 

 new genus, Trodes (see p. 390). 



Bomolochus ostracionis. — Richiardi in 1870 established a new 

 species which he referred to the genus Bomolochus, and which pos- 

 sessed similar prehensile hooks. He describes them as follows: 



All' estemo dell' inserzione del primo articolo delle antenne del primo paio, si 

 staccano dalla superficie del cefalo-torace due gross! uncini robusti, rigidi, i qiiali si 

 prolungano indietro fino oltre le antenne del secondo paio quasi paralelli al margine 

 laterale del corpo, curvi nella loro lunghezza, a punta molto acuta, sul margine 

 intemo verso la loro base anteriormente presentano una piccola appendice unciniforme, 

 essi servono evidentemente all' aniniale a fissarsi suUe membrane sulle quali vive 

 paraesito (p. 53). 



He thus recognizes their function, but makes no further attempt at 

 an explanation of their presence. 



In endeavoring to locate his species he states at the close of his 

 paper that, from the presence of these two large hooks and from 

 the form and position of the maxillipeds, it ought to belong to the 

 genus Eucanthus of Claus. But in spite of this he places it under 

 the genus Bomolochus, giving as his reasons for so doing the shape 

 of the basal joint of the first antennae, the form of the mandible and 

 maxilla, the shape of the last joint of the endopod of the fourth legs, 

 and the number of body segments. But variations in shape and form, 

 especially within the narrow limits here described, are manifestly 

 specific in value and not generic. Furthermore, the only difference 

 in the number of body segments is found in the abdomen where 

 variety is the rule among all the parasitic copepods. Such differ- 

 ences as these can not offset the presence of maxillary hooks and the 

 structure and position of the maxillipeds. Hence the species mani- 



ProcN.M. vol.39— 10 27 



