ART. 20. TWO NEW INTESTINAL. TKEMATODES TUBANGUI. 7 



17807) contain a second lot of specimens also collected by Dr. R. T. 

 Shields from the intestine of a dog in Nanking, China, in 1913. 



Odhner (1913) considered his genus Prohemisto7num an interme- 

 diate group between the typical Holostomes and the genus Cyatho- 

 cotyle Muehling, 1897, partly because of the incomplete division of 

 the body, externally, into an anterior and a posterior region. With 

 Cyatjiocotyle it has been placed in the subfamily Cyathocoty- 

 linae by Railliet (1919), but so far no generic diagnosis has been 

 given.^ The inclusion of P. industrium in Prohemistomum brings 

 together species exhibiting two types of clinging plugs as in the 

 genus Alaria {^=iHeinistoinu7ri) . P. spinulosuTii and P. appendicu- 

 latuni have clinging plugs of one type, their clinging plugs being 

 of small size, round to oval in shape and with or without a central 

 depression. P. industrium has a clinging plug of another type, its 

 clinging plug being very extensively developed and dome-shaped and 

 occupying at least two-thirds of the body length. 



Genus PROHEMISTOMUM Odhner, 1919. 



Generic diagnosis. — Alariidae : Small trematodes, not over 2 mm. 

 in length, more or less oval in shape, with the body not distinctly 

 divided into an anterior and a posterior region. The cuticle is pro- 

 vided with spines or with fine scales. The anterior lateral margins 

 of the body are foliaceous and rolled meso-ventrally to form ventral 

 folds which unite posteriorly. Between the ventral folds and behind 

 the acetabulum is a clinging apparatus which takes the appearance of 

 a round or oval, knob-like process, which may or may not present a 

 central depression; or that of an extensively developed plug which 

 reaches anteriorly so as to hide in ventral view the acetabulum, 

 pharynx and even the oral sucker. The simple intestinal branches 

 extend almost to the posterior extremity of the body. The smooth 

 or slightly indented testes lie one behind the other in the posterior 

 half of the body or they may occupj^ the greater part of the body 

 length between the acetabulum and the posterior end of the body. 

 An elongated cirrus sac enclosing the vesicula seminalis and cirrus 

 lies ventral to the testes. The small, globular ovary is found ventral 

 to the anterior testis, opposite the cirrus sac. The diffuse shell gland, 

 vitelline reservoir and the junction of the ootype and Laurer's canal 



=> Railliet (1919) subdivided the Holostomata into five subfamilies, namely, Stiigoinae, 

 Alariinae, Cyathocotylinae, Polyotylinae (Polycotylinae), and Braunininae. The family 

 Strigeldae was proposed to include these subfamilies, so that at present there exist 

 the following terms which refer to the same group of trematodes : Holostomidae, Diplo- 

 stomidae, Hemistomidae, and Strigeidae. To avoid confusion which is apt to arise by 

 the use of many synonymous names, I would favor the adoption of Hemistomidae against 

 the rest for two reasons : the species represented by Hemistomum are better known and 

 tliey appear to occupy a central position among the Holostomata. It has been pointed 

 out, however, by Krause (1914) and by Hall and Wigdor (1918) that the name Alaria 

 has priority over Hemistomum, so that the family name Alariidae should be used in place 

 of Hemistomidae. 



