2 PROCEEDING!^ OF THE NATIONAL MJJISEVM. vol.53. 



in the present paper, because of the opportunity thus afforded for 

 comparison and inference. 



A. Scott (1901) and Sir William Turner (1905) are the only 

 authors who have verified the internal anatomy of the species they 

 described by means of sections; the others have relied entirely upon 

 what could be seen through the body walls. Scott described Ler- 

 naeocera hranchialis, while Turner portrayed Pennella halaenopterae^ 

 representatives of two of the four subfamilies. In the preparation 

 of the present paper various species of the genera Lernaea^ Ler- 

 naeenicvs, Peniculus, and Collipravus have been studied by means 

 of serial sections, thus supplementing and completing the work of 

 Scott and Turner. 



It was further found after trial with various reagents that if 

 specimens were properly dehydrated in absolute alcohol and entirely 

 cleared in clove oil, they became so transparent that the internal 

 anatomy in all its details was clearly visible without sectioning. 

 Nearly every species described in the present paper has been treated 

 in this manner, and the internal specific and generic characters have 

 been thus determined. 



Hence the systematization here proposed is the result of a careful 

 study of the life history and of both external and internal mor- 

 phology, and is substantiated by serial sections. 



Much of the work was done at the laboratory of the Bureau of 

 Fisheries at Fairport, Iowa, during the summers of 1914, 1915, and 

 1916. 



That portion of the work which concerned the genus Lemaea^ 

 which is parasitic upon fresh-water fishes, and the material for which 

 was collected at Fairport, has already been reported to the United 

 States Bureau of Fisheries. The remainder of the work is incor- 

 porated in the present paper, and as here constituted the family 

 Lernaeidae includes 17 genera, three of which — Gardiodectes, Colli- 

 pravus, and Trifur — are new to science, and 80 species, of which 15 

 are new. There are seven generic names which have been intro- 

 duced into this family, each of which is composed of the name 

 Lernaea or the corresponding adjective Letmalos and some other 

 word. Two of these compound names, Lernaeopoda and Lemaeomy- 

 zon, belong in the family Lernaeopodidae ; two others, Lemaeonema 

 and Lernaeo'penna, are synonyms; the remaining three, Lernaeenicus, 

 Lernaeocera, and Lernaeolophus, are still valid genera in the present 

 famih\ In the author's opinion, the first part of all these names 

 should be spelled alike, since each represents the same word which 

 was in existence and whose spelling had been determined long before 

 any of the compounds were formed. 



