98 NEW GYEODACTYLOID TEEIIATODES FROM AUSTRALIAN FISHES, 



very distinct vagina is present, opening on the ventral surface near the right 

 side of the animal in the vicinity of the body constriction. The lumen of the 

 vagina, on its distal half, is strengthened with a very prominent chitinous lining 

 which extends posteriorly into a definite receptaculum seminis which gives o£E a 

 short narrow pouch to the right. The viteUaria are vei-y well developed, lying 

 above and below the intestinal limbs which they embrace over their whole length. 

 The transverse yolk-duct is clearly visible at a considerable distance in front 

 of the ovary, and at its middle is dilated into a distinct yolk-reservoir. No ripe 

 eggs were present in the material available. 



Found on the gills of the marine black-spotted goat fish, Upeneus signatus 

 Qunther, from Moreton Bay, S.E. Queensland. 



12. D A I T R E o s o M A, n.gen. 



TetraoncMnae in which the disc is not very sharply marked ofE from the 

 body. Fom- large hooks present on disc, together with a pair of minor hooks. 

 Body markedly constricted into a short anterior and long posterior portion. In- 

 testinal caeca absent. Intestinal limbs communicating behind. Vagina present. 

 Cirrus a long thin tube. Ovary and testis not lobed. Yolk does not extend 

 into the posterior third of the body. 



Found on the gills of freshwater fishes of the genus Therapon. 



Type species, D. comtrictum, n.sp. 



Daiteeosoma consteictum, n.sp. (Plate xii., figs. 15-19; xiii., fig. 20.) 



This worm measures about .45 mm. in length, .16 mm. in greatest breadth. 



The anterior third of the body is marked off by a deep constriction from 

 the posterior two-thirds, giving the woitn a characteristic appearance. In general 

 shape the pai-asit-e varies considerably according to the state of contraction; if 

 uneontracted there appears a long, rather narrow, posterior portion which bears 

 the disc, but if well-contracted, the worm may be oval. 



The disc which is not very shai-ply marked off from the body, bears two 

 pairs of large hooks, the ventral pair being much the larger and more strongly 

 curved, lying in a pair of postero-ventrally directed lobes of the body wall (PI. 

 xii., fig. 16). At their bases they articulate with a large transverse chitinous 

 bar and each with a small anteriorly and slightly inwardly directed chitin-pieee, 

 on which the well developed longitudinal muscles are in part inserted. The 

 dorsal hooks are more slender and not so strongly curved. They ai-e directed 

 upward, the ventral hooks downward. At the side is a pair of small lateral 

 lobes, each armed with a very small chitinous hook. 



The body cuticle is smooth. The longitudinal muscle-layer has undergone 

 great development in the ventral region to form a pair of longitudinal muscles, 

 arising below the ovary and inserted, at their distal end, into the hook apparatus 

 of the disc. These two muscles are joined by a second longitudinal pair lying 

 internally to them and converge proximally in the vicinity of the posterior end 

 of the intestine. These muscles form definite projections on the ventral body- 

 wall. 



The mouth is situated median- ventrally ; the pharynx is prominent, broader 

 than long and there is no definite oesophagus. The intestinal branches pass 

 backward, approach each other in the region of the body constriction, then 

 diverge again, but join immediately behind the testis. Intestinal caeca are 

 absent. Ventrally, immediately behind the constriction, there are on either side 

 two large masses of heavily-staining tissue which appear to open into the in- 



