402 MARSHALL ; HABITAT OF MONTACUTA FERRUGINOSA. 



is only by the lump of sand breaking open in a favourable posi- 

 tion that the whole arrangement can be seen, and it scarcely ever 

 varies from this ; but on one occasion I found a wandering 

 Moiitacuta in a spadeful of sand without an echinoderm near 

 it, and it was probably seeking a host or admission into a family 

 of its own kind. I also on another occasion found a Montacuta 

 actually within the small circle of spines fringing the ventral 

 end of its host, but not adherent. 



I have no doubt the remaining 40 per cent, also had their 

 followers, but they could not be found owing to the difficulty of 

 opening the sand exactly in the line of the burrow, and of 

 course if not parted exactly at the right angle it is almost im- 

 possible to find it afterwards by breaking up the sand further or 

 by stirring it about, especially with a rising tide at one's heels. 



Again, from another part of South Devon, where the sand 

 is soft and sloppy, I find the Echinocardium affords a home for 

 Montacuta ferruginosa ; but here the former rise to the surface 

 on the approach of the tide. They not only rise to the surface, 

 but if the sun is hot and the tide low, they appear impatient 

 for its return, and will travel about on the surface for a yard 

 or two, in a very ungainly fashion, dragging the Montacuta. in 

 its track by a byssus about half-an-inch in length, though the 

 immature ones are more closely attached, or embedded at the 

 base of its spines. They are also more plentiful in this district, 

 a dozen being sometimes met with on a single echinus, and in 

 one instance I counted eighteen, but never more than one adult 

 to each echinus. In this locality the latter may be leisurely 

 watched creeping about on the sloppy surface, drawing in and 

 ejecting sand and water, and dragging the larger Montactdce in 

 its track, but sometimes leaving younger ones on the way. It 

 will thus far be noted that in four separate localities M. ferru- 

 ginosa adopts methods of seeking its living in close proximity 

 to echinoderms. 



I have alluded to the curious circumstance that no two of 

 each group of Monfacufce are of the same size. They cannot 



J.C, vi,,Oct., iSqi, 



