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656 R. C. PUNNETT.whilst the oesophagus at this level is very small. The genital pleurae are still large in thisregion but become much reduced shortly after it.Ptychodera viridis, n. sp. (PL XXX VII. figs. 2, 6, 7 ; PI. XXXIX. fig. 32; PI. XLII.figs. 17 and 19).Locality, etc. From Hulule, Maldive Is. Three specimens only, two being complete,were dug from sand towards the cast of the island.External features. Coloured sketches from life of this worm were fortunately madeby Mr Forster Cooper. From the reproductions of these on Plate XXXVII. it will be seenthat green is the prevailing tint on the body of the animal, though the j)roboscis is paleyellow, and the collar pale yellow with a certain amount of orange. To the predominantbody tint the animal owes its specific name. From the sketches it appears that the proboscisis considerably longer than the collar, a proportion which still exists in the preserved creature.The length is not great. Of the two complete specimens one measured 36 mm. and thesecond only 21 mm. in length after preservation (ratio of total length to collar length beingrespectively 18 : 1 and 14 : 1). Compared therefore with such forms as Pt. flava, var. laccadivensis,this sjjecies is a small, short, and somewhat stunted form. The genital pleuraeare well-developed. The external liver saccules are relatively feebly developed and are ofa uniform colour.Internal structure. The musculature of the proboscis is strong and compact, theradial bundles into which the longitudinal muscles are gathered being closely connected byconnective tissue. The powerful development of the longitudinal muscles leads to the practicalobliteration of the proboscis cavity (PI. XXXIX. fig. 32). A well-marked dorsal musculardecussation occurs in the anterior part of the proboscis (PI. XXXIX. fig. 32, dmd) andfibres from it pass ventral to the central complex. Dorso-ventral muscles anterior to thepericardium are not present. The ventral proboscis septum reaches forwards almost to thetip of the stomochord. The racemose organ is small and unlobulated. Both proboscis poresare present though only one is in functional communication with the dorsal proboscis coelom.This may be either the right or the left one.Collar. The musculature and the connective tissue are here strongly developed andthe cavity of the collar is very much reduced. The dorsal septum occurs after the firstroot as usual and is generally complete. Traces of the ventral septum may occur. Thelumen of the collar cord is almost entirely obliterated throughout and the cord in sectionhas as great a dorso-ventral diameter as a lateral one (PI. XLII. fig. 19). In one of thespecimens sectioned three roots were present of which the last was rudimentary.The cornua of the nuchal skeleton apparently vary much in length. In one specimenthey extended over about ^ of the collar, whilst in another they were rather more than aquarter as long as this structure.Trunk. The branchial region is short. Compared to the collar length as unity itmeasured in the three available specimens -85, I'OO, and 1-44, giving an average of 110.The branchial portion of the oesophagus is approximately of the same size as the ventralportion. The post-branchial groove is very ^hort and insignificant. The genital folds arelarge in the branchial region and also in the region of the post-branchial groove (PL XLII.fig. 17).