110 R. C. PUNNETT. 



A frontal organ is present. Numerous small eyes occur, chiefly on the dorsal surface 

 and just beneath the basement membrane. Head glands not well marked. 



8. Cerebratulus ischurus, n. sp. (PL V. fig. 7.) 



Locality. Hulule, Male atoll, Maldive Is. From reef 



Fragments of a single specimen amounting to 21 cm. in all. The oesophageal region 

 is rounded in shape, and the breadth here is about 7 mm. The intestinal region is some- 

 what flattened, and shews a well-marked median ventral longitudinal groove. It measures 

 about 14 mm. in width and about 5 mm. in depth. No record has been preserved of the 

 colour in life. After preservation it is a uniform pale dirty brown. 



The epithelium is thin, and contains a few unicellular gland cells. The basement 

 membrane is very thin, and beneath it is a fine layer of circular muscle fibrils and then 

 some longitudinal fibrils separating the last named from the cutis glands. The last are 

 not well developed. The structure of the body wall bears a great resemblance to that of 

 C. haddoni (Punnett, Proc. Zool. Soe. 1900, PI. LV. fig. 8), from which it differs in the some- 

 what greater development of the cutis glands. 



The muscles of the body wall are strongly developed. The outer longitudinal layer is 

 about half as thick again as the circular layer. This in its turn is about double the 

 thickness of the inner longitudinal layer. There is a thick layer of longitudinal muscles 

 between the probo.scis sheath and oesophagus. It is continued round the oesophagus as a 

 delicate investment of longitudinal muscle fibrils. 



The mouth commences at the hind level of the dorsal ganglion and lies below the 

 cerebral organ. 



The vascular system in the snout shews a system of lacunar anastomosing spaces in 

 lieu of a well-marked head loop. The hinder part of the cerebral organ is surrounded by 

 a blood lacuna. The oesophageal lacunae are spacious. 



The proboscis is slender. It is two layer as regards musculature, and shews two 

 muscle crosses. The wall of the proboscis sheath is remarkably muscular. Its circular 

 muscle layer is just over half the thickness of the circular muscle layer of the body wall. 

 There is also a delicate outer investment of longitudinal muscle fibrils continuous with the 

 layers separating the proboscis sheath from the oesophagus and circular musculature of the 

 body wall respectively. 



The excretory system commences some way behind the mouth. The tubules extend 

 ventral to the nervous side stems and also dorsally to the proboscis sheath. In the anterior 

 fragment cut there was but one excretory duct. Judging from other forms, it is exceedingly 

 probable that had more excretory ducts been present some would have occurred in the 

 comparatively large number of sections through the excretory region. Consequently it is 

 probable that C. ischurus is a form with but one pair of excretory ducts. 



The brain is small compared with the bulk of the animal. The fibrous core of the 

 dorsal ganglion is about twice the size of that of the ventral ganglion. The dorsal nervous 

 commissure gives off a median dorsal, which for a very short distance behind the brain lies 

 in the outer longitudinal muscle layer, and not between it and the circular layer as is 



