NEMERTEANS. 107 



compared with the size of the worm. Between the dorsal surface of the oesophagus and 

 the proboscis sheath a few longitudinal muscle fibres are present. There is no diagonal 

 muscle layer. A few horizontal muscles occur over the mouth. 



The opening of the mouth is situated just before the level where the cerebral organs 

 terminate. The oesophagus is comparatively small and becomes exceedingly constricted 

 posteriorly. 



The vascular system shews a well-marked cephalic loop (PI. V. fig. 9). The buccal 

 commissure is very large. The oesophageal lacunae unite, directly behind the nephridia, to 

 form a single small lateral lacuna on either side, which eventually passes into the lateral 

 vessel. The last named is distinguished from the lacuna by the fact that it has an outer 

 lining of parenchyma cells and gives off small dorsal vascular commissures to the median 

 dorsal vessel at regular intervals. The median dorsal vessel leaves the proboscis sheath 

 just after the termination of the excretory system. 



The proboscis is unfortunately lacking. Judging by the small size of the rhynchocoelom 

 it could not have been very large. It was attached very far forwards to the dorsal wall 

 of the sheath just behind the excretory region. 



The excretory system is small and confined to the anterior region of the oesophagus. 

 The tubules extend both dorsally and ventrally to the level of the nervous stems. About 

 the centre of the system there is a single excretory duct (PI. V. fig. 9) on either side 

 which makes an angle of about 4.5° with tbe level of the nervous stems. 



No gonads are to be distinguished. 



The brain is well developed and the dorsal ganglion is double the size of the ventral. 

 Both in the brain and in the nervous side stems the internal fibrous core is more 

 strongly developed than usual. For this reason the nervous side stems are larger and more 

 conspicuous in transverse section than is usually the case, and their large size may possibly 

 be connected with the unusually thick body musculature. A large neurochord cell is present 

 on the ventral and inner surface of each ventral ganglion soon after its separation from 

 the dorsal ganglion. The median dorsal nerve is not well marked. The dorsal brain com- 

 missure is short and rather stout. The cerebral organ (PI. V. fig. 6) is large and ovoid 

 in shape. The glands developed in connection with it are somewhat scanty. It lies at 

 first directly above and then to the inner side of the nervous stem. The head slits reach 

 nearly to the brain. They continue deep a little way after the ciliated canal has been 

 given off. 



A frontal organ is present. Eyes are absent. The head glands are very scanty. 



G. Cerebratulus maculatus, n. sp. (PL IV. fig. 1, and PI. V. figs. 1, 5, 10.) 



Locality. Suvadiva atoll, Maldive Is. Dredged from 45 fathoms on mud bottom. 



Represented b}' fragments of a single specimen amounting to 62 mm. Average breadth 

 about 3 mm. Anterior end somewhat rounded, posterior portion much flattened. Hind end 

 lacking. The colour of the preserved specimen is a pale brownish-yellow marked with black 

 spots. These markings are short broken transverse lines in the anterior oesophageal region. 

 A short distance further back they become round, whilst still further back in the posterior 

 oesophageal and intestinal regions they become short longitudinal markings. They are 

 present both on the dorsal and on the ventral surface. (PI. IV. fig. 1.) 



14—2 



