404 A NATURALIST ON THE "CHALLENGER." 



these birds and their allies hatched their eggs by means of the 

 heat derived from decayed vegetable matter. 



We shot a small Cuckoo, with a beautiful greenish golden 

 metallic lustre on its feathers (Centrococcyx viridis), in the 

 bushes. On the shore were inclosures built by the Moros as 

 fish traps, to retain fish as the tide receded. In the shallow 

 water contained in these traps were a large number of Medusce 

 all lying on the tops of their umbrellas, with their tentacles 

 directed upwards in full glare of the sun. They looked thus 

 posed like a lot of Sea- Anemones, and I took them for such at 

 first. They appeared perfectly lively, and from time to time 

 contracted their umbrellas ; It appeared almost as if they had 

 assumed their position voluntarily, and were waiting for food in 

 the same manner as Actinias. 



Alcyonarians (social Polyps, distinguished by having eight 

 tentacles), are extraordinarily abundant about the beach of Santa 

 Cruz Major. The reef rocks are covered with the soft spongy 

 forms of Alcyonarians ; they form extensive beds, which are 

 soft and boggy to tread on in wading. Amongst these grows a 

 stony coral, which is likewise Alcyonarian, as I found to my 

 astonishment on examining its minute structure. It forms 

 thick erect plate-like masses which are of a chocolate colour 

 when living. The coral is remarkable because its hard cal- 

 careous skeleton is of a bright blue colour instead of white, as 

 usually the case. The coral is hence named Heliopora ccerulea. 

 It is, as far as is known, the only surviving representative of a 

 large number of extinct forms of Palaeozoic age, which are 

 familiar in the fossil condition. It is nearly allied to the well- 

 known Eed Coral of commerce.* 



Again, another interesting Alcyonarian is abundant, together 

 with those just described, namely, the red Organ-Coral [Tubipora 

 musica). There were cartloads of this coral, dead and dried, 

 lying on the beach, which was entirely composed of various 

 coral dibris. The " Organ- Coral " was not to be found living in 

 shallow water on the reefs, but living specimens were dredged 

 from a depth of ten fathoms. 



* H. N. Moseley, " On the Structure and Relations of the Alcyonarian 

 Heliopora Ccerulea, &c." Phil. Trans. R Soc, Vol, 166, Pt. 1. 



