The zooids are extremely contractile and only a few fully expanded ones were obtained. They measure up to 11 mm. in length and 0.7 mm. in width in the pharyngeal region and are characterised by a narrow post-abdomen occupying two-thirds of the body length. Six short triangular lobes surround the branchial aperture. The atrial aperture is surmounted by one or two small strongly-built muscular lappets. The wall of the pharynx is broken by twelve or thirteen rows of ten or eleven stigmata, three or four times as long as they are wide. Thirteen or fourteen bundles each containing two or three longitudinal muscle fibres run down the pharynx wall and continue right down into the post-abdomen, but show no tendency towards concentration on any side of the zooid. Three to six tranverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to at least two orders of size. The dorsal lamina is composed of twelve or thirteen long languets which curve back at the level of the third or fourth stigmata from the dorsal edge. The oesophagus is short and leads to a short rounded stomach with twenty-three to twenty-six longitudinal folds. The intestine continues backwards for a short distance before turning to run up towards the atrial aperture. In expanded zooids there are no marked constrictions of the intestinal wall, such as are figured by Michaelsen (1924, p. 393, Fig. 21a.)

The testis extends throughout the posterior half of the post-abdomen and consists of fifty-four to seventy-four lobes arranged in two parallel rows around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior half of the post-abdomen, a short distance in front of the most anterior testis lobes. Tadpoles undergo development within the mantle cavity in a type of brood pouch, the shape of which depends on the number of tadpoles present, and can hardly be used as a distinguishing feature, though Michaelsen gives it a certain amount of prominence in this species. Tadpoles (Plate 3, Fig. 4) are light yellow and were present from the middle of November, 1944, until the end of March, 1945. The largest tadpole measured 2 9 mm. in length and 0.9 mm. in width in the head region.

Distribution: In New Zealand—f. typica—Tauranga (Mich.), d'Urville Island (Sluit.), Otago Harbour; var. ptychodes Mich.—Stewart Island (Mich.) Elsewhere—f. typica—Chatham Islands (Sluit.).

Text Fig. 2.—Aplidium (Amaroucium) phortax. Right side of zooid. × 25.

Remarks: Although type specimens are not available, the differences between the description given above and Michaelsen's

description of A. phortax f. typica are such minor ones that the author feels justified in placing the Otago specimens in this species. The differences noted in the structure of the pharynx are probably due to the fact that more specimens were available in Otago, for in almost every case Michaelsen's figures come within the range given above, the exceptions being the number of stigmata per row (9, Michaelsen; 10 to 11, Otago specimens) and the number of branchial tentacles. However, as Michaelsen admits that the inner organisation of the thorax cannot be clearly stated due to the strong contraction of the zooids, these factors can be discounted. The only other difference is the absence of “Sternchenzellen” in the test. So far, var. ptychodes has not been seen in the Otago Harbour.

Aplidium (Amaroucium) adamsi n.sp. (Text Fig. 3; Plate 2, Fig. 4; Plate 3, Fig. 1.)

This species forms large fleshy masses on the under-surfaces of rocks, wharf piles, etc., in all three localities. The colonies are usually bright pink or orange in colour, but pale yellow and light pink specimens are also found. The largest colony measured was 15 cm. in the longest diameter. The height above the substratum ranges from 10 to 14 mm. at the edge of the colony to 25 to 35 mm. at the common cloacal apertures. Unevennesses of the surface are due primarily to mound formation around the common cloacal apertures, which are large (up to 5 mm. in the longest diameter), and are separated by distances of 0 9 to 1.8 cm. The zooids are arranged in irregular branching systems (Plate 2, Fig. 4.) The test is colourless, semi-transparent, of a soft gelatinous consistency, and undergoes no marked changes upon fixation in formalin. Throughout the entire test numerous small test cells and a few large round cells are present, and in the surface layers many white spicule-like structures are also found. These are rosette-like in appearance, 0.7 to 0 8 μ in diameter, and give no reactions when treated with acids or alkalis. The zooids have a brilliantly coloured pharynx, a pale yellow abdominal region, and a post-abdomen which is colourless except for the ovary, in which the ripe eggs are deep maroon.

Zooids measure up to 28 mm. in length and 1 0 mm. in width in the pharyngeal region and are characterised by a narrow post-abdomen occupying two-thirds of the body length. Six short triangular lobes guard the branchial aperture. The atrial aperture is surmounted by one or two long, wide lappets in which muscle fibres are very poorly developed or entirely lacking. The wall of the pharynx is broken by twelve or thirteen rows of nine or ten stigmata, four or five times as long as

Text Fig. 3.–Aplidium (Amaroucium) adamsi. Right side of zooid. × 20.

they are broad. Thirteen or fourteen bundles each containing one or two muscle fibres run down the pharynx wall and continue down into the post-abdomen, but show no tendency to concentration on any one side of the zooid. Three or four transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina is composed of twelve or thirteen long langucts which curvé backwards at the level of the third or fourth stigmata from the dorsal edge. The oesophagus is short and leads to a short rounded stomach with twenty-two to twenty-four longitudinal folds. The intestine passes backwards for a short distance before turning to run up towards the atrial aperture. There are no marked constrictions of the intestinal wall.

The testis extends throughout the posterior three-quarters of the post-abdomen and consists of forty-six to fifty-six lobes arranged in two parallel rows around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior quarter of the post-abdomen, a short distance in front of the most anterior testis lobes. Tadpoles undergo development within the mantle cavity and the shape of the pouch so formed depends entirely on the number of tadpoles present. Tadpoles (Plate 3, Fig. 1) are bright orange and were present from the beginning of November, 1944, until the end of March, 1945. The largest tadpole measured 4 3 mm. in length and 1.1 mm. in width in the head region.

Distribution: Otago Harbour.

Remarks: This species is distinguished from A. (A.) phortax f. typica by:—

Added to that, although colour varieties of the two species are found in Otago Harbour, the fact that no intermediate forms occur marks them clearly as two different species.

This species is distinguished from A. (A.) phortax var. ptychodes by:—

From a survey of the literature of the genus the author can find no species with which it is identical and has decided to name it Aplidium (Amaroucium) adamsi after Mr. W. Adams, who has been associated with the Portobello Marine Biological Station for many years.

Type Specimen: Otago Museum.

Aplidium (Amaroucium) benhami n.sp. (Text Fig. 4; Plate 2, Figs. 1, 4; Plate 3, Fig. 3; Plate 5, Fig. 1.)

This species forms small colonies on the under-surfaces of rocks and on the fronds and holdfasts of seaweeds in all three localities. The colonies are very conspicuous on account of the brilliant orange coloration and the stellate arrangement of the zooids (Plate 2, Figs.

1, 4). The test is free from sand grains. The largest colony measured 4.5 cm. in the longest diameter. The height above the substratum varies from 5 to 8 mm., but is almost uniform within the one colony. Common cloacal apertures are small (1.0 to 2.0 mm. in the longest diameter) and are separated by distances of 4.0 to 6.0 mm. They form the outlet for ten to eighteen zooids which are arranged around them in stellate or elongate oval patterns. The test is firm, orange, transparent, and contains many small test cells and a few large round cells, the latter being confined to the surface layers. In formalin the colonies fade to a dirty white and the arrangement of the zooids is lost. Orange pigment is present in all parts of the zooids. being concentrated in the eggs, and partly masked by an additional white pigment in the pharyngeal region.

Zooids measure up to 8 mm. in length and 0.9 mm. in width and are characterised by a wide post-abdomen (up to 0.65 mm. in width) occupying approximately one-half of the length of the zooid. Six short triangular lobes surround the branchial aperture. The atrial aperture is surmounted by three long, well-developed lappets, the central one of which is slightly longer than the others. The wall of the pharynx is broken by ten or eleven rows of fourteen to sixteen stigmata, five to seven times as long as they are wide. Bundles of not more than two longitudinal fibres run down the pharynx wall, but are not concentrated on any one side of the zooid. Three to five transverse muscle fibres are present between the rows of stigmata. Branchial tentacles are sixteen in number and belong to three orders of size. The dorsal lamina is composed of ten or eleven long languets which curve backwards at the level of the fourth or fifth stigmata from the dorsal edge. The oesophagus is comparatively longer than that of A. (A.) phortax and A. (A.) adamsi. It leads to a short rounded stomach with twenty-two to twenty-six longitudinal folds. The intestine passes backwards for a short distance before turning to run up towards the atrial aperture. There are no marked constrictions of the intestinal wall.

Text Fig. 4.—Aplidium (Amaroucium) benhami. Right side of zooid. × 25.

The testis extends throughout the posterior two-thirds of the post-abdomen and consists of twenty-eight to forty-two lobes arranged around the sperm duct, which runs straight up towards the atrial aperture. The ovary lies in the anterior third of the post-abdomen directly in front of the most anterior testis lobes. Tadpoles (Plate 3, Fig. 3) are bright orange and were present in the mantle cavities of specimens collected between the middle of November, 1944, and the end of February, 1945. The largest tadpole measured 3.4 mm. in length and 0 63 mm. in width in the head region.