1915] MacCallum: Ectoparasitic Trematodes 397 



family. These he named Diplectanum aequans, found on the gills 

 of Labrax lupus; Diplectanum pedatum on the gills of an un- 

 known fish of the Julis family, and Diplectanum echeneis on the 

 gills of Sargus rondeletii. However, other than naming them 

 he gave little or no description of the worms by which they might 

 be recognized. 



In 1862 Van Beneden and Hesse did the genus more justice, 

 but it was not until 1904 that it was much more completely de- 

 scribed by MacLaren, who has endeavored thus to make D. 

 aequans the type species. 



In 1862 Van Beneden and Hesse described the worm dis- 

 covered by them as D. sciaena from the gills of Sciaena aquilla, 

 one of the drumfish. 



Parona and Perugia discovered and described a form which 

 they called D. aculeatum. We have then thus far five members 

 of this sub-genus described as follows: 



Diplectanum aequans, Wagener, 1857, Diesing, 1858, 

 MacLaren, 1903 ; Diplectanum pedatum Wagener 1857 ; Di- 

 plectanum echeneis, Wagener, 1857; Diplectanum sciaena, 

 Beneden and Hesse, 1863 and 1864 ; Diplectanum aculeatum, 

 Parona and Perugia, 1890. 



In 1904, when Norman MacLaren wrote very fully upon D. 

 aequans, he also summed upon what had been written of the other 

 forms to that date. 



DiplectanuTYi teuthis, nov. sp.* 



(Fig. 132) 



On May 22, 1914, I found Diplectanum teuthis on the gills 

 of a Teuthis hepatus, a small worm of this species which differs 

 in many particulars from any of those hitherto described, con- 

 sequently I have ventured to name it D. teuthis and to call it a 

 new species. It is only .75 mm. in length by .10 mm. in width. 

 However, its anatomy is fairly distinct so that a reliable descrip- 

 tion may be given of it. 



*A11 of the forms described in this paper were found in material from the 

 New York Aquarium. 



