54 



MEMORANDA. 



hcsrens these average -j\-q of an inch m length, 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 -^-^ 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- 

 hcerens as an intruder ; while exactly opposite, on the Herm 

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

 abundantly. 



I hoped to find the remarkable molluscan genus Entocon- 

 chon, described by Miiller from S. 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, 



- A' //SUCKER 



New Parasitic Rotifer. 



/i-^''rj~:^ 



ISf?fl^\ 



Method of progression. 



Miliary spicule from tentacle of 

 S. inhmrens. 



Miliary spicules from tentacle of 

 (S. Sarniensis. 



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

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

 fa%oured me with a view of its expanded discs, and was ex- 



