BIOLOGY, MARINE — MAYER. II3 



of parasites, enough, I think, may be learned from the table to warrant the following 

 general remarks on the helminth fauna of the Tortugas. 



I shall record also in this connection a few extracts from notes made at the time the 

 material was collected. 



Acanthocephala. — Representatives of this order appear to be rare at the Tortugas. 

 The species found in the frigate mackerel was Echinorhynchtis fristis, which seems to be 

 eminently a southern form, since it was found to be the most frequently recurring 

 species at Beaufort, while a closely related species has a similar distribution in the fishes 

 of Bermuda. 



Neither in the fishes of Beaufort, Bermuda, nor Tortugas have I found Echinorhynchi 

 as abundant as in the fishes of northern waters. There thus appears to be the same 

 contrast between tropical and northern forms shown in the distribution of the Echino- 

 rhynchi as in many other groups of organic forms. In this case, however, there does 

 not appear to be a multiplication of species along with relative paucity of individuals, a 

 condition which is characteristic of many tropical forms. 



Nematodes. — But few nematodes were found. Those found in the nurse shark, a 

 species of Ascaris, were firmly attached to the stomach-wall, their heads penetrating at 

 least as far as the muscular layer. 



Representatives of the genus Heterakis were found sparingly in the green moray, gray 

 snapper, spot, and hogfish. Some of those from the gray snapper and one from the 

 spot agree closely with H. foveolata. 



A species of Ichthyonema was found on three different dates in the ovaries of the gray 

 snapper; one was also found in the gar. 



Immature nematodes were found, usually encysted on the viscera, in the following 

 fishes : Barracuda, yellow-grunt, yellow-tail, grouper, cabezote, French grunt, striped 

 grunt, black grouper, yellow-finned grouper. In all cases the number of these immature 

 nematodes was few. The most common type was characterized by having an elongated 

 basal bulb on the esophagus, and a diverticulum from the anterior end of the intestine. 



One very singular form was found in Iridio kirshii, which had a subglobular, chitinous 

 pharynx which was marked with spiral ribs running from left to right anteriorly, thus 

 crossing in optical section. 



Cestodes. — The larval forms usually referred to by the name Scolex polymorphus are 

 not so abundant as they would be in an equal list of northern fishes. Only a few were 

 seen and only in the gray snapper, yellow-tail, grouper, and frigate mackerel. 



Encysted stages, belonging for the most part to the genus Rhynchobothrium were 

 found in eight of tlie species of fishes examined. R. speciostim was recognized in a num- 

 ber of instances. Encysted cestodes were found only on the viscera. No cases of flesh 

 parasites comparable with that of the butter-fish (Poronotus triacanthus) of the northern 

 coast, or of the hound-fish (Tylosurus acus) of Bermuda, were met. The selachians 

 here as elsewhere are bearers of many species of adult cestodes, whose favorite place of 

 lodgment is in the spiral valve. 



I had the opportunity of examining but one sting-ray and that a small specimen. It 

 yielded, however, a list of nine species of cestodes belonging to seven genera. This list, 

 as identified at the time of collecting, is as follows : Acanthobothrium paidtim, Antho- 

 cephalum gracile, Phyllohothrium foliatum, Spongiobothriiim variahile, Synhothrium 

 aUcalle, and two species of Rhinebothrium and two species of Rhynchobothrium not 

 yet identified. It may be inferred therefore that the sting-ray, if a sufficient number 

 were to be examined, would yield as long a list of entozoa as it does at Beaufort or 

 Woods Hole. 



Some interest may attach to the fact that one lot of parasites is credited to the tiger- 

 shark in the table, although the shark from which they were obtained was not identified. 



8— YB 



