PLYMOUTH MARINE INVERTEBRATE FAUNA. 171 



shells, Pcden opercularis (abundant in patches), Sertidarella Gayi and 

 S. poli/zonias, Aglaophcnia myriopliyllwin, Cellaria sinnosa and C. fistulosa, 

 Ascidiella seahra, and Maovjjodia longirostris. 



Stoke Point Grounds. Western boundary, Blackstone Point ; 

 eastern boundary, Ifevelstoke Church Cove ; seaward extension, about 

 li miles. The ground shelves very regularly outside the 10-fm, line; 

 inside this line it is very uneven; maximum depth, 22 fms. 



In their general features these grounds present much similarity to 

 the 'Mevvstone grounds,' but they offer rather greater diversity of 

 type within a given area ; and perhaps partly as the result of this and 

 also of the fact that they are exposed to the full sweep of the Channel 

 tide, tlie fauna is considerably richer than it is on the Mewstone 

 grounds. 



The friable red rock characteristic of the Mewstone Ledge is met 

 with again, and forms numerous more or less detaclied reefs, off Stoke 

 Point. It is abundantly perforated by Flwladldea, and in the disused 

 crypt of this mollusc, the remarkable Ophiurid Opliiopsila aranea is 

 plentiful. As at the Mewstone, the surface of the rock is very clean, 

 and it affords attachment to Eunicella, Antenmdaria, Aglaophenia, 

 Alcyonium digitatum, Caryophyllia, Tcthya, etc. 



Between the reefs of red rock are patches of very rich shell sand and 

 gravel. 



The grounds include an eastward extension of the IMewstone 

 ' Echinoderm ' ground, together with patches where Ophiothriv and 

 Ophiocoma are abundant. In deeper water this gives place to typical 

 ' Clicdopterus ' ground. 



The Rame-Eddystone Grounds. This name has been used to 

 indicate the grounds lying for o to 4 miles on either side of the line 

 from Pame to Eddystone and at depths of from 25 to 30 fms. Two 

 typical classes of grounds can be recognised in this area: (1) coarse 

 grounds with a bottom soil of muddy gravel, on which Cha'toptcrv.s 

 is one of the most striking forms, and the chief Hydroids are Hidecium 

 halecinum and H. Bcani ; and (2) fine grounds with a bottom soil of 

 fine sand, characterised by the abundance of Cellaria sinuosa and 

 (J. fistidosa and by the Hydroid Sertidarella Gayi. Tlie grounds are very 

 patchy, and the two typical faunas are much intermingled, so that it is 

 only occasionally and after a short haul that a fair representation of 

 either of the two types of fauna is obtained. 



Both classes of ground can be profitably worked with both the dredge 

 and trawl. On both, Ecliinas oieulcntas and Fcdcn opercularis nuiy be 

 met with in large numbers in particular spots, and Asterias ri(bens and 

 A. glaoialis are generally distributed over the area. 



NEW SEKIES. — VOL. VII. Mt. 2. M 



