244 DR DOUGLAS'S ADDRESS. 



staged specimens there, that these productions were merely different 

 states of one species. The Halisarca of Dujardin, perhaps the lowest 

 of animal organizations, was noticed in much abundance and perfection ; 

 and we could easily imagine, that, by the addition of siliceous spicula, 

 immersed and crossed in its texture, it might become the Halichondria 

 panicea of Fleming, which grew alongside of it in several varieties. Of 

 the calcareous sponges, there were met with Ghantia coriacea, botryoides, 

 foliacea, and a singular variety of G. ciliata. Of Zoophytes, Coryne 

 squammata, Laomedea gelatinosa, Sertularia pumila, Lepralia COG- 

 cinea, Actinea mesembryanthemum, abounded, and in especial perfec- 

 tion and beauty. Of the Echinodermata, no other species than Echinus 

 esculentus, Ophiura fragilis and neglecta, occurred. The Echinus was 

 generally hidden by broken pieces of sea- weed, with which it covered its 

 shell. Of the Mollusca tunicata, there were many species remarkable 

 for their beauty^ but we can only specify the Ascidia rustica, Phallusia 

 intestinalis, and Aplidium ficus, for of the others the names could 

 not with certainty be determined. The calcareous stones were often 

 found perforated with Pholas crispata, and one stone was found by 

 Captain Mitford, with many of the shells still living hidden in their ex- 

 cavations. In one of these holes, a good specimen of Venus perforans 

 was found ; and the Saxicava rugosa was not uncommon. A great 

 number of specimens of LameUaria tentaculata of Montagu were taken, 

 shewing that the species is liable to considerable variation in colour, and 

 in the degree of roughness of the mantle. Several very minute indi- 

 viduals of the Doris tuberculata were taken up unnoticed, until after our 

 return home, and it is remarkable that in these, some of which were 

 an eighth of an inch in length, there was no appearance of branchiae. 

 Another member of the family Doridee occurred, which is without ex- 

 ception the most beautiful naked gasteropode we have seen ; its name 

 remains for future investigation. * 



Passing from the Haven, the party next crossed over a formation of 

 limestone* consisting of three beds, from three to four feet each in 

 thickness, which, at the point to the eastward of the north sands, assume 

 a singularly undulated appearance. Mr Skafe has given a very brief 

 description of these, and a figure, illustrative of their undulations, in 

 Raine's History of North Durham, p. 172. Thence we walked to the 

 Snook, to the spot where Mr Donaldson Selby is boring .for coal. Here 

 the party separated, one division walking towards the village in as di- 

 rect a line as possible, that they might have leisure to examine the 

 Priory, Church, and Castle ; an other set, bent on the murder of rabbits 

 and partridges,. wandered over the links and fields in many a devious 



