116 PROCEEDING!^ OF THE NATIONAL MUSEUM. vol.53, 



from an Exocoetus {E. volitans) but differs from ours (namely from 

 exocoeti) both in the older and the younger stages so much that we 

 may regard it as quite distinct" (p. 415). 



A careful comparison of LeSueur's figures and description with 

 those of Steenstrup and Lutken does not show any differences of 

 specific value. 



BlainvilHi has three horns, all of a length and quite short and the 

 neck is short and stout; exocoeti has only two horns while the neck 

 is long and threadlike. But neither of these differences nor both 

 of them are sufficient to separate the two species; much more accu- 

 rate and detailed descriptions must be given before we can definitely 

 establish them as distinct species, infesting the same host and in 

 the same locality. 



PENNELLA LIOUVILLEI Qnidor. 



Penella liouvillei Quidor, Deuxieme Expedition Antarctiqiie Frangalse, 

 Charcot, 1912, p. 209, pi. 1, fig. 1 ; pi. 2, fig. 2G ; pi. 3, fig. 28 ; pi. 4, fig. 37. 



Remarks. — This species of Quidor differs from exocoeti only in 

 the possession of a dorsal cephalic horn, in the branching of the 

 lateral horns, and in the fact that the inflated lateral portions of 

 the head do not project in front of the central portion. Quidor added 

 that the torsion was direct in exocoeti and inverse in liouvillei^ and 

 if we can judge from his text this is the difference which induced him 

 to establish his new species. But it has been shown elsewhere (p. lOD) 

 that torsion has no specific value, and the other differences might 

 all result from different conditions encountered while the parasite 

 was penetrating the tissues of its host. Hence there is need of more 

 details here also before the species can be definitely established. 



PENNELLA ANTARCTICA Qaidor. 



Plate 15. figs. 119-124. 



Penella antarctica Quidor, Deuxieme Expedition Antarctique Frangaise, 

 Charcot, 1912, p. 206, pi. 1, figs. 15-17 ; pi. 4, figs. 29, 34. 



Host and record of specimens. — Two females out of a lot that were 

 tsiken from the Sei whale, Balaenoptera horealis, off northern Japan 

 by Dr. R. C. Andrews of the American Museum of Natural History, 

 New York City, were presented to the National Museum and have 

 received Cat. No. 47820, U.S.N.M. 



/Specific characters of female. — Head distinctly separated from the 

 first thorax segment by a deep groove, ellipsoidal with the long 

 diameter transverse, and flattened somewhat dorsoventrally; divided 

 into two halves by a longitudinal furrow, which is wide and shallow, 

 beginning at the antennae on the dorsal surface, extending around 



