462 MOLLUSCA OF MAST HEAD REEF, QUEENSLAND, I., 



interested in finding a species of Bonellia in abundance in the 

 lagoon. Though already reported from Sydney Harbour* and 

 Cambridge Gulf, W.A.,t this genus has not yet been recorded 

 from Queensland. The sporadic occurrence of Bonellia, Pocillo- 

 pora, and similar tropical forms near Sydney, is probably due to 

 the warm southerly current. Swept down by this, the Australian 

 Gulf Stream, these northern forms incessantly attempt to 

 colonise our coast, but perish. 



In the space of a week no collectors, however diligent or expert, 

 would expect to exhaust their station. The subsequent catalogue 

 is not likely to enumerate more than half, if indeed as much, of 

 the total molluscan fauna. The collection studied is presented 

 to the Australian Museum. 



Little is known of the minimum temperatui'e corals can endure. 

 The attention of visitors to this archipelago in spring or winter is 

 especially invited to this subject. We had hoped to regularly 

 record sea surface temperatures, but the distance to which the 

 water retreated from our camp at low tide impeded our observa- 

 tions. The lowest reading registered was 65° Fahrenheit. 



For the following observations I am indebted to Mr. Skeet : — ■ 



Outside the reef, October 23rd, 7 a.m., the sea surface tempera- 

 ture was 74° Fahrenheit. 



In the lagoon, October 24th, 6.30 a.m., water 70°; 7 pm., air 

 73°, water 75°. Oct. 25th, 9 a.m., air 74°, water (high tide) 67°. 

 3.15 p.m., air 75°, water 78°; 9 p.m., air 68°, water 69£°. Oct. 

 26th, 7.15 a.m., water (half-flood) 65°; 8 p.m., air 70°, water 72°. 

 Oct. 27th, 7.45 a.m., air 75°, water (half-ebb) 69°; noon, air 85°; 

 water 76°. Oct. 28th, noon, air 85°, water (high tide) 77°. Oct. 

 30th, noon, air 85°, water 75°. 



In conclusion I would express my thanks to my companions, 

 who, whatever their interests or occupations, were always on the 

 look out for shells for me. I am especially indebted to Miss L. 

 Parkes, who kindly undertook the wearisome task of sifting the 



* Haswell, these Proceedings, x. 1886, p. 331. 

 f Saville Kent, Proc. Roy. Soe. Q'land, vi. 1889, p. 230. 



