Oll two new Araphistorae parasites of Sumatran fishes. 669 



At the extreme posterior end tliere is a large sucker which in tlie 

 averag:e individual measures 1,2 mm in breadth, the apertiire measur- 

 ing 4 mm. There is on the ventral surface at a point 0,8 mm 

 beilind the mouth in the median line the aperture of the genital 

 cloaca. Otherwise the skin is quite tense and smooth except for 

 the orifice of the excretory apparatus which lies just in front 

 of the posterior sucker in the median line dorsally, and the 

 minuter orifice of Laurer's canal which may he seen a short 

 way fnrther forward also in the median dorsal line. The skin sliows 

 a fine netw^ork of anastomosing lines, apparently cuticular canals. 

 which unite on the ventral surface into four trunks one at each 

 margin, and one on each side of the midline ventrally about half 

 way out to the margin. These converge anteriorly about the mouth. 

 About the posterior sucker tliese canals are especially abundant. 

 There is no armature of cuticular spines. The orifice of the mouth 

 is quite small being terminal and surrounded by concentric folds of 

 skin but not showing externally any definite sucker-like arrangement. 

 There is, however, a moderately strong sucker which is somewhat 

 deeply embedded in the tissue and which is particularly characteristic 

 in tliat it possesses two lateral muscular pouches. These are about 

 as large as the sucker itself and have quite tlie same muscular 

 .structure. It seems, therefore, most reasonable to regard them as 

 sucking Pouches although Walter in describing DipJodiscus sub- 

 davatns, interprets them as salivary glands. These pouches lie 

 dorsally and between and below them there lies the Oesophagus 

 which opens backward from the mouth cavity. This is short giving 

 rise almost at once to the curious elongated muscular pharynx. In 

 this the alimentary canal is narrowed to a very fine epithelium-lined 

 tube which is surrounded by many dense concentric layers of muscular 

 or elastic tissue. Outside this there are abundant cells closel}^ 

 applied to the concentric lamellae. Most of them are rounded or 

 cuboidal or irregulär nucleated masses, but there are some large 

 vacuolated cells with large vesicular nuclei which look almost like 

 ganglion cells. At about the level of the genital cloaca the pharynx 

 goes over into the intestine proper which divides into two lateral 

 coeca which run toward the posterior part of the body and end 

 blindly a short way in front of the posterior sucker. While the 

 Pharynx is lined with cuticle the intestinal coeca have a lining of 

 cubical epithelial cells which are. however. provided with long eilia 

 so uniform in length and so thicklv matted together that the mucosa 



