54 



MEMORANDA. 



heerens these average -j^j^ of an inch in lengthy and are 

 much branched and broken up at either end ; in S. Sarnien- 

 sis, on the other hand (in which the large wheel and anchor 

 plates are the more ornate), the miliary spicules are very 

 small, irregularly oblong rods, quite simple in form, and 

 averaging -3-^ of an inch in length. This is a most de- 

 cisive differentia, and may be thoroughly depended on. It 

 is a curious, and to me inexplicable fact, that S. Sarniensis 

 occurs only on the Guernsey shore, with an occasional S. in- 

 h(Rrens as an intruder ; while exactly opposite, on the Herm 

 shore, four miles distant only, 8. inhcerens occurs, and very 

 abundantly. 



I hoped to find the remarkable molluscan genus Entocon- 

 chon, described by Miiller from *Si. digitata, in the Guernsey 

 Synaptse, but in a rather hurried examination failed. I, how- 

 ever, found a very remarkable parasite in the body-cavity of 

 both the Channel-Island species in very great abundance. 



Miliary si^icule from tentacle of 

 (S. inhcBrens. 



New Parasitic Rotifer. 



Z-'-r.™ 



Method of progression. 



Miliary spicules from tentacle of 

 S. Sarniensis. 



namely, a Rotifer. In the figure is given all that I could ascer- 

 tain of the structure of the parasite at that time. It never 

 favoured me with a view of its expanded discs, and was ex- 



