I 



330 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 2 



considerable biological interest especially in comparison with the trema- 

 tode fauna of the tropical Atlantic. This aspect of the study will be con- 

 sidered in a separate paper. 



Practically every digenetic trematode collected is accounted for in 

 this paper with the exception of immature specimens and several species 

 of Didymozoonidae. The latter, usually encysted, were not favorably 

 preserved for specific identification. Numerous specimens (and several 

 species) of immature distomes corresponding to the Distomum fenestra- 

 tum of Linton were collected. Some of these at least are probably identi- 

 cal with the Atlantic forms. 



Unless otherwise indicated, measurements are in mm. In most cases, 

 usual terminology descriptive of trematodes is followed. The term "fore- 

 body" is used to refer to that portion of the body anterior to the acetab- 

 ulum. Nicoll's term "ecsoma" is used for the tail appendage of hemi- 

 urids. Lloyd's (1938) term "pre-somatic pit" is used for the ventral pit 

 of certain hemiurids. Following the pars prostatica in many trematodes 

 is a swollen region (inside or outside the sinus sac or the cirrus sac) 

 with tall transparent cells. Manter (1934) refers to this structure as a 

 "prostate vesicle." Although Park (1936) has called it a "cirrus vesicle," 

 the term "prostatic vesicle" is used in this paper. Its function is unknown. 



The collection and study of these parasites were made possible by the 

 kindness and co-operation of Captain Allan Hancock and the Carnegie 

 Institution of Washington, D.C. Most of the study was made at the 

 University of Nebraska. The manuscript was completed in 1939 at the 

 Rocky Mountain Biological Laboratory. The writer wishes to express 

 appreciation to Dr. Waldo Schmitt for many kindnesses and favors in 

 connection with the work. Considerable technical assistance in preparing 

 specimens and in routine work on the manuscript was rendered by stu- 

 dents employed under the National Youth Administration at the Uni- 

 versity of Nebraska, especially by Miss Rita Giesken. 



ASPIDOGASTREA Faust and Tang, 1936 



Aspidogastridae Poche, 1907 



Lobatostoma pacificum, new species 



(Plate 32, figs. 1, 2) 



Host: Trachinotus paloma Jordan and Starks 

 Location: Intestine 

 Locality: Charles Island, Galapagos 

 Number : Many. 52 specimens were mounted 



