8 PROCEEDIN-GS OF THE NATIONAL MUSEUM VOL.73 



1915, January 7. 104. Dimensions in formalin: Length 2.25; 



diameter of head, including spines, 0.45, of 

 neck 0.30, of body at middle 0.70, near 

 posterior end 0.22. 



HIMASTHLA ELONGATA (Mehlis) 



Figures 17-20 



1831. Distomum elongatum Mehlis, Isis, p. 177. 



1892. Echinostomum elongatum (Mehlis) Stossich, Boll. Soc. adriat. Sc. nat. 

 Trieste, vol. 13, p. 39. 



1909. Distomum elongatum (Meblis) Dietz, Zoolog. Anzeig., vol. 34, p. 184. 

 Himasthla elonga (Mehlis) Dietz, Die Echinostomiden d. Vogel. Inaug. 



Diss., Konigsberg, p. 16. 



1910. Dietz, Zoolog. Jahrb., Suppl. 12, pp. 360-363, pi. 13, fig. 25. 



La'i^s argentatus^ L. inarinus^ L. ndibundus. 



Woods Hole, Mass. : Larus argentatus, L. delawarensis, L. marinus^ 

 L. Philadelphia^ Nycticorax nycticorax, intestine. 



These distomes, while they vary considerably in size and propor- 

 tions, appear to belong to the same species, and are in such close 

 agreement with H. elongata that it seems best to refer them to that 

 species in spite of the difference in the number of circum-oral spines. 



H. elongata is characterized by having 29 circum-oral spines, of 

 which the two which are situated at each angle of the oral disk are 

 smaller than the others. In all the specimens in Avhich they could 

 be distinctly seen in the Woods Hole material, the number of oral 

 spines was found to be 31, arranged as shown in Figure 18. Further- 

 more, there is little difference in the length of the spines. The 

 apparent difference in the camera lucida sketches is due to fore- 

 shortening. 



Body slender, nearly linear, neck spinose, concave on ventral side ; 

 oral sucker ventro-terminal, small, surrounded by a reniform, spine- 

 bearing disk. The circle of spines is interruped below so as to have 

 a somewhat horseshoe shape. The number of oral spines is 31, of 

 which 27 are around the border and 2 at each posterior angle of 

 the disk. The spines differ little in size, the length being about 

 0.054, breadth 0.014. Pharynx near the oral sucker, longer than 

 broad ; esophagus slender ; rami of intestine begin at anterior border 

 of ventral sucker and extend to the posterior end of the body; 

 ventral sucker much larger than oral, in some cases nearly circular 

 in outline, in others longer than broad. Genital pore on median 

 line at anterior border of ventral sucker; cirrus long and covered 

 with spines; cirrus-pouch elongate and posterior to ventral sucker, 

 with a spacious seminal vesicle at its posterior end. In a series of 



