456 Records of the Indian Museum. [Vol. VIII, 



comparatively stout build measuring from 3 mm. to 4 mm. in 

 thickness, a measurement which includes the raised ambulacral 

 surface of the ventral side. 



It is not easy to assign any definite position in the body for the 

 mouth and genital aperture, but there is very little error in stat- 

 ing that, in the larger animals, the mouth is about half-way along 

 the ventral surface; in the smaller specimens, the mouth is 

 considerably further back, approximately two-thirds from the 

 anterior end. The genital aperture is not very far removed from 

 the mouth and its position is best described as being 7 mm. to 

 10 mm. behind it. As a rule both apertures were clearly visible, 

 though in two cases the most careful examination failed to reveal 

 more than one aperture. 



The ground colour of the dorsal surface in the living animal 

 is described by Mr. Kemp as a ' dull reddish brown ' ; the pre- 

 served animal presents more of a yellowish brown, frequently, 

 however, with a reddish tint at the sides of the body. Occasion- 

 ally a distinct bluish shade is to be observed ; closer scrutiny 

 shows that it is the deeper tissues that are a very dark greenish 

 blue, and this colour can be seen through the brown ; where the 

 outer tissue has been removed by injury, the clear greenish blue 

 is well shown. Thus in one or two cases a variety of colour is 

 shown by an indiscriminate distribution of light blue, dark blue, 

 green and various shades of brown. 



Along the mid-dorsal line runs a thin dark line from the 

 head to the caudal extremity, which usually widens very slightly 

 above the regions of the mouth and genital aperture. In some 

 specimens there is just a suspicion of a lateral darker band at 

 the edge, much broader than the median line, and only to be seen 

 in certain parts; this, not being constant, must be regarded as a 

 variation. A little distance inwards from the posterior edge 

 of the lobes of the head is a dark line not usually so prominent 

 as the median line (see fig. i). 



The ventral colouration in the living animal is described 

 by Mr. Kemp as brownish pink with a pale ambulacral surface, 

 the head being somewhat dusky. In the preserved animal, the 

 general surface is a light creamy brown or light biscuit colour ; 

 at the edges, the reddish (in some cases greenish) tint of the 

 dorsal surface encroaches in the form of a seam. The head is 

 always a little darker than the rest of the ventral surface. 

 From the neck to the extreme posterior, in the mid- ventral line, 

 is the whitish ambulacral surface, forming a prominently raised 

 ridge, rather less than one-third the width of the body ; in the 

 region of the pharynx and genital organs it is somewhat wider ; 

 anteriorly, it is flat, and the shading gives, as in B. giganteum, 

 a remarkable arrow-head appearance (see fig. 6). 



Eyes surround the entire fringe of the head and lobes, 

 and are continued round to the sides of the neck where they 

 form a black patch ; they are extremely numerous, and at the sides 

 of the neck are much more closely approximated than on the head. 



