16 Papers from the Marine Biological Laboratory at Tortugas. 



describe such details of structure as I was able to make out from the 

 living material and supplement it with further details obtained from 

 stained and mounted specimens. In many cases I was able to get fairly 

 satisfactory series of sections, in which case such details as seemed to 

 me to be of service in identification, or which appeared to be new, were 

 added. Since this paper contains mention of all the trematodes which 

 I found while at the Tortugas laboratory, it is unavoidable that many 

 of the descriptions will be incomplete in some particulars. If the paper 

 were intended simply as a contribution to systematic zoology, only 

 those forms would have been included which were represented by abun- 

 dant material or by material in good condition for study. Since my 

 purpose is to make a contribution to the knowledge of the helminth 

 fauna of the Dry Tortugas, the paper should be regarded as bionomic 

 in intention while largely systematic in form. 



On account of the many new forms which are described, a key to 

 the genera and species has been prepared, which, together with the 

 figures, it is believed will make it possible for future workers to recog- 

 nize most of the forms readily. 



One trematode, Deontacylix ovalis, was found which I do not rec- 

 ognize as having any near resemblance to any family, and I have there- 

 fore made it the type of a new suborder Deontacotylea (figs. 231-235). 

 I have also added the family name Siphoderidce to accommodate cer- 

 tain trematodes with an anterior oral and a ventral genital sucker. 

 The Allocreadiince are well represented and some very interesting prob- 

 lems in morphology are suggested. Prof. H. S. Pratt proposes to take 

 up the morphological study of this and other groups. The field is cer- 

 tainly a rich one. Especially suggestive is the singular trematode fauna 

 of the black angel-fish (Pomacanthus arcuatus), some of the genera of 

 which bear a strong resemblance to genera which are characteristic of 

 turtles. 



Attention is here called to an interpretation of certain cells, espe- 

 cially abundant in the neck of many distomes, but found elsewhere less 

 abundantly. These appear to be yolk-forming in their function. They 

 are mentioned in the descriptions of a number of the distomes described, 

 but the best example is that afforded by Deradena ovalis; see especially 

 fig. 169. 



For a cheerful readiness to compare notes and to confer upon ques- 

 tions of classification, I should be remiss if I did not take this opportu- 

 nity of thanking Professor Pratt, who spent the season of 1909 at the 

 Tortugas laboratory, where he began studies on the morphology of the 

 trematodes. 



I must especially express my obligations to Dr. Alfred G. Mayer, 

 whose invitation led me to investigate the rich and interesting helminth 

 fauna of the Dry Tortugas, and whose unfailing courtesy made my 

 sojourn there most enjoyable. 



