Internal Anatomy (Plate 115, fig. 2)

The septa ix/x, x/xi, xi/xii and xii/xiii are muscular and thickened.

Alimentary Canal. There is a strongly muscular pharynx in i–iv. A thin-walled proventriculus lies in v and vi. It is much larger than is usually the case in the Megascolecidae. The proventriculus passes into a very thick-walled muscular gizzard which occupies vii. The oesophagus passes through viii–xvii and bears a single pair of prominent calciferous glands in xv. The intestine commences in xviii.

Vascular System. The dorsal blood vessel is paired throughout its length. A slender unpaired supra-intestinal blood vessel extends through x-xiii and gives rise to a pair of hearts in each of those segments.

Reproductive System. There are two pairs of testes, a pair in x and a pair in xi, attached to the anterior septum of each segment close to the ventral mid-line, and a pair of ovaries in a similar position in xiii. The testes and ovaries have a similar form, each organ consisting of a cluster of short, thread-like processes projecting freely into the coelomic cavity of the segment. There are two pairs of large spermathecae, a pair in viii and a pair in ix. Each consists of a large dorsoventrally flattened oval sac opening by a slender duct to the exterior. Three small diverticula open into the upper part of the duct close to the spermathecal sac (Plate 115, fig. 3). A pair of prostates lies in each of segments xvii and xix. The prostates are extremely convoluted tubular organs, each opening by a narrow muscular duct to the exterior. There are neither penial chaetae nor copulatory muscles in the prostatic segments. A pair of vesiculae seminales occurs in each of ix, x, xi and xii. Those of xi and xii are of a racemose form and occupy most of the coelomic cavity of the segments, while those of ix and × are more compact, smaller structures, attached to the posterior septa of their respective segments.

A band of small micronephridial tubules is found on the lateral aspect of the peritoneum on each side of each segment except the first.

Octochaetus sylvestris n.sp. (Plate 116, figs. 1–3)

A number of specimens of this light pink earthworm were collected from Kopua silt loam in an area of native rain-forest (rimu, matai, lancewood, rata) at Wakarara station, Central Hawke's Bay.

The specimen on which this description is based is 87 mm. in length and 4 mm. in diameter, with 154 segments.

The prostomium is tanylobous. The clitellum is buff in colour and prominent, covering the dorsal and lateral surfaces of segments xiii–xvii. The first six segments have no secondary annulations, but vii and all the segments posterior to vii are biannulate.

There are eight chaetae on each segment, arranged in pairs. On segment xxiv: