. Bulletin of the British Museum (Natural History) Zoology. 50 S. PRUDHOE 2 <» " •. Paradiscocelis furcata: A, arrangement of eyes anteriorly; B, sagittal section of copulatory organs. chamber; pharynx with several pairs of shallow lateral folds lying in mid-third of body. Common genital pore lies shortly posterior to pharynx and leads into a spacious genital atrium containing open- ings of male and female ducts. Male complex not yet fully mature, so only a partially-developed structure can be described. The male copulatory complex is invested with a very thick mass of muscle-fib
. Bulletin of the British Museum (Natural History) Zoology. 50 S. PRUDHOE 2 <» " •. Paradiscocelis furcata: A, arrangement of eyes anteriorly; B, sagittal section of copulatory organs. chamber; pharynx with several pairs of shallow lateral folds lying in mid-third of body. Common genital pore lies shortly posterior to pharynx and leads into a spacious genital atrium containing open- ings of male and female ducts. Male complex not yet fully mature, so only a partially-developed structure can be described. The male copulatory complex is invested with a very thick mass of muscle-fibres. An ejaculatory duct appears in the antero-dorsal region of this musculature and is lined with a ciliated epithelium, but it is not possible to determine whether a seminal vesicle will be formed later. In the middle of the muscular mass, the ejaculatory duct widens into a small vesicle lined with glandular cells, suggesting that the vesicle might later function as a prostate. This vesicle gives off two limbs, one directed anteriorly and the other posteriorly. The anterior limb opens into the anterior region of the genital atrium through a wide depression on the ventral surface of the muscular mass, whereas the posterior limb opens through a thick protuberance into the atrium near the genital pore. At each end of the muscular mass lies a pair of relatively large fusiform glandular organs, and between the two pairs a number of pyriform prostatoids lie beneath the surface of the mass and open into the atrium. The latter is wide, but much compressed dorso-ventrally. No penis-papilla has been made out. From the hind wall of the genital atrium, the vagina extends posteriorly and terminates in a crescentic Lang's vesicle with anteriorly-directed limbs. The vagina has not yet developed a 'shell'-chamber, but about midway along its length, it receives a common uterine canal. Genus TETRATREMA Definition. Discocelididae, Body elongate oval. Marginal eyes extend posteriorly
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