44 THE VOYAGE OF H.M.S. CHALLENGER. 



this coat is just beyond the proboscidian canal, while the thinnest part is in the median 

 line above it. 



" The proboscidian sheath has a remarkably thick wall, which is chiefly composed of 

 an interwoven circular coat, presenting an irregular looped appearance in transverse 

 section. The fibres in thin sections seem to anastomose. On the inner surface of this 

 coat are some longitudinal fibres, with a glandular epithelial coat internally. 



" Posteriorly the body-cavity is greatly dilated by the presence of a vast series of ova, 

 so that all the muscidar coats are much thinned, and the digestive canal contracted. The 

 inner longitudinal coat is especially affected, three thickenings only being left, viz., one 

 on each side of the proboscidian sheath, and one in the middle line ventrally. The ova 

 are compressed into various angular forms, between vertical partitions which occur at 

 short intervals in the region, and which fill up the entire area, except the small space for 

 the proboscidian and digestive canals superiorly." 



For some farther particulars concerning this species, I refer to the description of Cere- 

 bratulus macroren that is still to follow, and where the points of agreement and of differ- 

 ence between these two evidently closely related species will be more fully entered upon. 



A second specimen, also from the New Zealand waters, shows that the conspicuous 

 development of the secondary basement layer of the integument, and the considerable 

 thickness of the medullary nerve, are further characteristic features of this species. 



Cerebratulus angusticeps, n. sp. (PI. I. fig. 15 ; PI. XIV. figs. 1, G ; PI. XV. fig. 4). 



This is another Schizonemertean from the New Zealand waters (Station 167a, Queen 

 Charlotte Sound, June 27, 1874 ; 10 fathoms). Its head is figured on PI. XV. fig. 4. 

 In MTntosh's preliminary notes this fragment is referred to in the following words : — 



" A fragmentary form, resembling in shape C. angulatus, and with an acutely pointed 

 snout. The diameter of the widest flattened region is about 4 "5 mm. The colour is dull 



yellow, with a darker stripe down the middle of the dorsum The vascular 



trunks lie opposite the nerve-cords, and this in the angular lateral region. The external 

 longitudinal muscular coat is largely developed, and the fibres are uniformly fine. The 

 very much produced lateral angle of the body is mainly composed of this coat. In such 

 forms the lateral nerve-cord seems to be much flattened from above downwards." 



The sections which I made of this fragment, horizontally through the head and trans- 

 versely through the trunk, were in many respects very instructive. To the flattened and 

 pointed shape of the head they added an internal distinctive feature of the species in the 

 unusual size of the posterior brain-lobes, which, although in intimate connection with 

 the superior brain-lobes in the same way as in the Schizonemertea, in general equalled 

 or even surpassed the latter lobes in length. PL XIV. fig. 6, gives a representation of 

 this, illustrating, at the same time, how in a horizontal section the blood-space (c.o.l.) 



