RAMBLES OF A GEOLOGIST. 465 



able one. He showed me a collection of flags, with which 

 he intended constructing a grotto, and which contained nu- 

 merous specimens of Coccosteus, that he had exposed to the 

 weather, to bring out the fine blue efflorescence, a phosphate 

 of iron which forms on the surface of the plates. They re- 

 minded me, from their peculiar style of colouring, and the 

 grotesqueness of their forms, of the blue figuring on pieces 

 of buff-coloured china, and seemed to be chiefly of one spe- 

 cies, very abundant in Orkney, the Coccosteus decipiens. We 

 next walked out to see a quarry in the neighbourhood of the 

 manse, remarkable for containing in immense abundance the 

 heads of Dipteri, many of them in a good state of keeping, 

 with all the multitudinous plates to which they owe their 

 pseudo-name, Polyphractus, in their original places, and bear- 

 ing unworn and untarnished their minute carvings and deli- 

 cate enamel, but existing in every case as mere detached 

 heads. I found three of them lying in one little slaty frag- 

 ment of two and a half inches by four, which I brought along 

 with me. Mr Clouston had never seen the curious arrange- 

 ment of palatal plates and teeth which distinguishes the Dip- 

 terus ; and, drawing his attention to it in an ill-preserved 

 specimen which I found in the coping of his glebe-wall, I re- 

 stored, in a rude pencil sketch, the two angular patches of 

 teeth that radiate from the elegant dart-head in the centre 

 of the palate, with the rhomboidal plate behind. " We have 

 a fish, not uncommon on the rocky coasts of this part of the 

 country," he said, " the Bergil or Striped Wrasse (Labrus 

 Bcdanus), which bears exactly such patches of angular teeth 

 in its palate. They adhere strongly together ; and, when 

 found in our old Pict's houses, which occasionally happens, 

 they have been regarded by some of our local antiquaries as 

 artificial, an opinion which I have had to correct, though 

 it seems not improbable that, from their gem-like appearance, 

 they may have been used in a rude age as ornaments. I 



2 G 



