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



The longitudinal muscles are slightly pleated, the transverse muscles not at all. There 

 is a special muscular cord on the same side as the transverse muscle, which extends close 

 to the wall, becomes broader as it runs downwards, and is homologous in position with the 

 parietobasilar muscle of other Actiniae. Further, it appears to me that all the septa 

 reach the oesophagus, are all furnished with reproductive organs (in the present instance 

 with testes), and have all a small perioral and a very large marginal opening (fig. 12). 

 Unfortunately I could not decide this point with any certainty, as only a few septa, 

 such as that given in fig. 1 2, could be dissected out ; most of them were sticking 

 together so that the mode in which the reproductive organs were distributed on the septa 

 was never clearly seen in transverse sections. 



Tribe III. Monaule^e. 



Actiniaria with paired septa, but with only one pair of directive septa. 



The Monauleae form the third and last group in which the paired arrangement of the 

 septa is distinctly pronounced, and therefore come nearer to the Hexactinise and 

 Paractiniae than the Zoanthese and Cerianthese. It is remarkable that there is only one 

 pair of directive septa, a fact which may perhaps be explained by the obliteration of 

 the second pair. 



From the absence of the second pair of directive septa, it follows that the body is 

 exactly bilaterally symmetrical, as it is divided into symmetrical halves by only one 

 divisional plane which runs through the intraseptal space of the directive septa. This 

 divisional plane passes through an interseptal space on the opposite side, and divides the 

 remaining pairs of septa equally, half lying on its right and half on its left. The whole 

 number of the pairs of septa is consequently unequal. 



There is only one oesophageal groove, caused by the marked shortness of the directive 

 septa, and on account of this I have chosen the name Monauleaa (auXos, a groove or tube). 

 This groove was not very distinct, however, in transverse sections in the species examined ; 

 it would probably come out more clearly if looked at from the surface. 



As I only know one species, it would be little to the purpose to give special diagnoses 

 for the family and genus. I shall therefore proceed at once to discuss the species. 



Family, Monaulid^e, Hertwig. 



Scytopliorus, n. gen. 1 



Scytophorus striatus, n. sp. (PI. III. fig. 6 ; PI. XIII. figs. 1, 3, 8). 



Sessile Monaulidse with seven pairs of septa and fourteen longitudinal furrows on the 



1 sxi;T£>?=leather. 



