Helminth Fauna of the Dry Tortugas. 163 



this parasite abundant and varying from young specimens a few millimeters 

 in length to adults with ripe segments and measuring as much as a meter in 

 length. There were also large numbers of ripe proglottides free in the chyle 

 of the intestines. Furthermore, I have never seen this cestode in its adult 

 stage, in any other host than the tiger-shark. 



Since tiger-sharks are rather common in the waters about the Tortugas 

 this vicarious identification is probably correct. 



In like manner the finding of the cestode Discocephalum pileatum in the 

 cub-shark, while not justifying a change in any record of habitat, at least 

 calls in question the validity of a former identification. 



This species was based on four specimens obtained from material brought 

 to the laboratory of the United States Fish Commission at Woods Hole, 

 Massachusetts, July 19, 1886, and taken from what was reported to me to 

 be a dusky shark (CarcliarJiiiius obscnrus}. The viscera only were brought 

 to the laboratory. 



No other entozoa were found associated with them. Twelve specimens 

 were found on another occasion in a shark which was identified as a dusky. 

 They were associated with a few examples of Anthobothrium laciniatum 

 and Orygmatobothrium angnstiim. In all other specimens of dusky shark 

 which I have examined at Woods Hole I have found numerous cestode 

 parasites. As a rule there were several different species, usually repre- 

 sented by numerous examples, in each shark. The same conditions were 

 found to prevail in the dusky sharks which I examined in 1901 and 1902 at 

 Beaufort, North Carolina. 



The third find of D. pileatum was made in 1903, when I collected seven 

 specimens from a cub-shark (C. platyodon) in Bermuda. In that case also 

 the worms were not associated with any other cestodes, and the heads, as in 

 the first instance, were firmly attached to the walls of the intestine. These 

 conditions were repeated very closely in the cub-shark which was examined 

 at Tortugas. The single specimen of D. pileatum was firmly attached to 

 the intestinal wall, the disk-like head being embedded in the submucosa. 

 There were, however, associated with this specimen, five other minute ces- 

 todes, representing four species and as many genera. They were Antho- 

 bothrium laciniatum, Phoreiobothrium lasium, Otobothriurn crenacolle, and 

 another which was not identified at the time of collecting and concerning 

 whose systematic position I am not yet certain. 



Leaving the species D. pileatum out of the account, it will be observed 

 that two of the above species, viz, A. laciniatum and P. lasium, have been 

 found in the dusky shark, both at Woods Hole and at Beaufort, and one 

 other (0. crenacolle} at the latter place. While there is thus established 

 a close resemblance between the cestode parasites of the dusky and the 

 cub-shark, the species D. pileatum must, at present, be regarded as a parasite 

 of southern range and of rare occurrence in the dusky shark. 



Trematodes. Beyond the preliminary examination made at the time of 

 collecting, and often of necessity hastily given, the collection has not been 

 studied. 



From notes made during the preliminary examination it would appear 

 that there are about 33 species, many of which are new. Of these, all but 

 nine could be referred to the old genus Distomum. Three species of Gas- 

 terostomum were noted. Appendiculate distomes were seen in but two in- 

 stances, one in the green moray and the other in the Spanish sardine. Those 

 from the moray were numerous and resembled the form which I have been 



