NEMATODA 



549 



figures are evidently very diagrammatic. He records the species from the small intestine 

 of Mustelus plebejus (= M. vulgaris). Orley (1885 a) gives a somewhat fuller description 

 of material from M. vulgaris and il/. laevis, but this is unfortunately in Hungarian, and 

 his German summary (1885 b) contains only the statements that the spicules of the male 

 are short and slender, and that there are 16 pairs of caudal papillae. 



The length of the present specimen is 24-5 mm., and its maximum thickness about 

 0-65 mm. The cuticular striations are too fine and faint to measure. The oesophagus is 

 just over 2 mm. long, including a spherical, posterior, non-muscular ventriculus 

 measuring 0-23 mm. in diameter. The muscular oesophagus proper is club-shaped. It 



oes. 



01 MM 



Fig. 6. Acanthocheilus qiiadiiden- 

 tattis. Anterior end of female, 

 dorsal view. 



Fig. 5. Acanthocheilus quadri- 

 dentatus. Anterior end of 

 female, dorsal view, c.p., 

 cervical papilla; /., intes- 

 tine; n.r., nerve-ring; oes., 

 oesophagus ;t'., ventriculus. 



is surrounded by the nerve-ring at 0-55 mm. from the anterior extremity. There is no 

 intestinal caecum running forward by the side of the oesophagus, nor is such a structure 

 mentioned by Molin or by Orley, though in another species, A. nidifex Linton, 1900, 

 such a caecum is said to be present. At a point 0-67 mm. from the anterior end there is 

 a pair of small, button-like cervical papillae. The excretory pore is probably close to the 

 base of the ventro-lateral lips. 



Molin describes each of the three lips as having a single median papilla, while 

 Orley also appears to refer only to three cephalic papillae. In the present specimen the 

 dorsal lip bears a pair of lozenge-shaped papillae, while on each ventro-lateral lip one 

 such large papilla is present towards the ventral border. It is uncertain whether or not 

 there is a smaller papilla near the lateral border. Each lip bears on its inner surface the 



