6 PEECY SLADEN TETJST EXPEDITION. 



The epithelium, such as remains, rests on a fairly stout basement-membrane, 

 immediately under which is the pigment. A thick layer of cutis-glands rests upon an 

 equally thick gelatinous layer. The head-glands are well-developed and extend in the 

 longitudinal muscle-layer as far behind the end of the mouth as this itself is behind the 

 tip of the snout ; they are found ventrally as well as dorsally, aud in section appear as 

 a broken ring in the outer longitudinal muscle-layer. 



The circulatory system shows the cephalic lacuna characteristic of this genus. 



The lateral nerve-cords are somewhat more ventral than is usual. 



The state of preservation renders it impossible to deal satisfactorily with the excretory 

 system. 



The numerous eyes extend back as far as the brain-region. 



The proboscis is two-layered and is without muscle-crosses. 



7. Baseodiscus sordidus, sp. n. (Plate 1. fig. 9.) 



Locality. Praslin, Seychelles, from the reef. 



Length 200 mm., breadth in the oesophageal region 4 mm. Colour when preserved 

 in spirit a dirty green. 



The epithelium rests upon a distinct basement-membrane, under which occur circular 

 and a few longitudinal muscles. The layer of cutis-glands is well marked, and is 

 approximately the same thickness as the gelatinous layer. Both epithelium and cutis 

 appear to contain some pigment. 



In internal structure this species is of the usual Baseodiscus type. There are many 

 excretory ducts on each side. The head-glands reach just past the cerebral organ and 

 are dorsal only. The eyes are small and numerous. 



8. Baseodiscus longissimus, sp. n. 



Locality. Zanzibar (Crossland Coll.). 



Several specimens of a very long white form, in general shape resembling B. hemprichii. 

 The length of one complete specimen was over 800 mm., the breadth averages 3-4 mm. 



The structural points which seem to separate this species from other members of the 

 genus are as follows: — The head-glands are well marked and stretch some distance 

 behind the brain, where they lie in the longitudinal muscle-layer ; viewed in section they 

 completely encircle the circular muscle-layer, but are most strongly developed dorsally 

 and ventraUy. The proboscis-sheath is comparatively short, extending through not more 

 than a quarter of the length of the worm. The proboscis itself is feebly developed, but 

 contains both circular and longitudinal muscle-layers. 



The exci'etory tubules are not connected by ducts passing to the exterior, such as 

 usually occur in the group. There are, however, slender ducts which place the excretory 

 system in communication with the gut *. 



* A similar condition is known to occur in the following other members of the genus : — B. quinquelineatus 

 (Punnett, Q. J. M. S. sliv. 1000, p. 113), B. indicus (Punnett, Fauna & Geogr. Maid. & Lace. Arch. i. pt. 1, 

 pp. 102, 104), B. civguhitus (Coe, liiol. Bull. 1906). In connection with the last species the author has gone into 

 the question in some detail. 



