AND PORTO SANTO. 15 



but which I found, on referring to my extracts, to be the teredo 

 gigantea, so accurately figured in Home's Comparative Anatomy : I 

 was surprised to find, however, that the longest did not measure 

 more than four inches ", which was also the ordinary length of the 

 t. navalis ; they had all bored in the direction of the grain of the 

 wood. A small crab, fig. 3, a and b, which I conceive to be a new 

 species o^ planes, was found in great numbers amongst the anatifera". 

 I kept a small net constantly floating for molluscae, but neither 

 caught nor saw any ; and, although we shot several water-birds 

 long before we made Porto Santo, they all floated past out of 

 reach. The phosphorescence of the sea was evidently produced 

 by a pink rotifera, wliich we fished up in buckets, and which re- 

 newed its expiring light whenever the water was agitated, but did 

 not induce any difference of temperature in it, as far as I could 

 judge by an ordinary thermometer. I could not help remarking 

 that our approach to the island, both before and after we saw it, 

 was not accompanied by alga of any description ; indeed, there 

 are very few to be met with in Madeira, probably, from the ex- 

 treme depth of the sea close in to the shore : a small frond of green 

 ulva was brought to me, (adhering to a piece of coralline) which 

 I also saw on the rocks, just raising their heads out of the sea, 

 between Funchal and Brazen-head, or Garajao. A species of 

 sertularia proper was dragged up, close to these rocks, which seems 

 to form an exception to the general character of the horny stem, 

 it being calcareous ; the colour was a dead white, and it was 

 attached to a mass of earth and coraUine, by a root hke that of a 

 fucus ; on peeling off the calcareous matter, a stem, also hke that 



" It was a cream coloured, transparent white, with a hght brown streak down the 

 middle ; the valves calcareous, of an uneven surface, and white. 



° It was of a delicate, but bright, rose colour : from the symmetrical form of its 

 test (notched so regularly as to increase the projection and distinctness of its chaperon,) 

 it may be called p. clypeatus. 



