BY T. HARVEY JOHNSTON AND 0. W. TIEGS. 97 



fourteen minor hooks. Head with two pairs of head-lobes. Body slightly con- 

 stricted neai- mid-region. Eyes absent. Intestinal limbs devoid of caeca and 

 without a tei-minal junction. Vagina with chitinous lumen. Testis and ovary 

 lying in the mid-line and occupying tlie posterior third of the mid-region of the 

 body of the worm. Penis large, not simple. 



From the gills of marine fishes. 



Type species, H'aliotnema australe J. & T. 



Halioteema australe, n.sp. (Plate xi., figs. 10, 12, 13, 14.) 



Length of adult .64 mm.; maximum breadth .24 mm. The disc is distinctly 

 marked off. Two pairs of head lobes are present. Slightly in front of its mid- 

 region the body undergoes a definite constriction which is not so pronounced, 

 however, as in Daitreosoma. 



The disc bears two pairs of large hooks (PL xi., figs. 10, 12), each with 

 a vei-y distinct biramous basal portion whose roots are connected by a very de- 

 finite and apparently chitinous membrane, complete except in one small place . 

 neai- the point of origin of the roots. The supporting chitin bai-s are two in 

 number and slightly crescentic in shape, the convexity of the bars articulating 

 with one another. Fourteen minor hooks are present, distributed as shown in 

 PI. xi., fig. 10. Of the body musculature the longitudinal layer is fairly well 

 developed; behind, the fibres concentrate to forai the muscles of the disc. Dis- 

 tinct circular fibres are absent, but there is a slight development of oblique 

 muscles. 



The mouth is a small transverse slit, lying ventrally at a considerable dis- 

 tance behind the anterior termination of the worm. The pharynx is large and 

 distinct. Leading into the short, conical buccal cavity are two pairs of gland- 

 cells. Into the short oesophag-us open the ducts of a number of digestive 

 glands ; but in the specimens available the exact connections of these glands 

 could not be observed. The intestine is bifurcated, the limbs approaching each 

 other slightly in the region of the body constriction but diverging again behind. 

 No junction takes place between the limbs posteriorly. Caeca are absent. 



Situated in each side of the head, and stretching considerably behind the 

 pharynx, is a mass of gland-cells. Their ducts were not visible, but they ap- 

 pear to be connected with the head-organs which lie in the first lobe of the 

 head. It is possible that some of the posterior gland-cells supply the pharynx 

 or oesophagus. Eyes are absent. The brain lies immediately in front of the 

 pharynx. 



The testis is a large solid organ lying between the intestinal limbs, almost 

 at the posterior end of the animal. The vas deferens passes forward as a wide 

 tube opening in the region of the body constriction into the vesicula seminalis. 

 The latter, which is a fairly large structure with strongly lobed outer margin, 

 extends forward almost as far as the beginning of the intestine, then bends 

 back upon itself and continues as a large vas deferens which inins beside the 

 penis and opens into it behind. The penis is a very distinct chitinous tube, 

 lying slightly obliquely and enclosed in a fairly distinct penis-sac. It consists 

 of two parts, a posterior simple tube, which appears to have a distinct articula- 

 tion with an anterior portion, the latter, at its distal end, developing into a 

 curious chitinous structure shown in PI. xi., fig. 14. 



The ovary is much smaller than the testis, in front of which it lies. 0\a 

 are prominent in its anterior region. The oviduct is a fairly wide tube,^ but 

 only its proximal portion could be seen. Shell-glands could not be detected. A 4 /S 



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