ON A NEW SPECIES OF ENTEROPNEUSTA . 85 



A new Species! of Enteropneusta, Ptyclwdera pelsarti *, from the Abrolhos 

 Islands. By W. J. Dakin, D.Sc, F.L.S., Professor of Biology in the 

 University of West Australia. 



[Percy Sladen Trust Expedition to the Abrolhos Islands under the 

 leadership of Prof. W. J. Dakin.] 



(Plates 10 & 11.) 



[Read 6th April, 1916.] 



Introduction. 



Notwithstanding the investigations that have been made up to date, the 

 coast of Western Australia is almost an unknown region so far as marine 

 biology is concerned. No Enteropneusta were known from this side of 

 Australia — as a matter of fact, none have been recorded from the north, 

 west, or southern coasts of the island continent. It was particularly 

 interesting, therefore, to find a number of specimens of an Enteropneust 

 on one of the Abrolhos Islands. The specimens were discovered by the 

 author of the paper on the lagoon side of the Pelsart Island Reef at its 

 southern extremity. It was originally intended to publish an account of 

 the islands before any papers on the fauna. As the work was, however, 

 rather of the nature of a preliminary examination, and a second expedition 

 is intended this year, the description of the islands will be withheld until 

 our return. 



At the place where the specimens were found the coral reef is submerged 

 at high-tide and only just uncovered at low- water. The rise and fall of the 

 tide is only about 2-3 feet. The specimens occurred in a deposit of sand, 

 gravel, and shell-fragments, which had collected in hollows in the smooth 

 water- worn reef-flat. They were frequently found under small loose pieces 

 of coral, with the anterior extremity just projecting out of the sand., About 

 fifteen specimens were obtained by sifting the gravel between the fingers 

 under water. They varied somewhat in size, but none could be called small, 

 the average size being about 4 inches (10 cm.) when extended. 



The specimens belong to a new species of the genus Pti/cJwdera. They are 

 not very far removed from some of the varieties of Ptycliodera flava now 

 known, and at first there was some doubt in my mind as to whether this new 

 form might not better rank as a subspecies. As, however, it appears quite 



* The species is named after Pelsart, whose ship was wrecked on the Abrolhos Islands in 

 the year 1629. The island on which the specimens were found is also named after Pelsart, 

 whose adventures at the Abrolhos Islands were of the most thrilling character. 



LINN. JOURN. — ZOOLOGY, VOL. XXXIII. 7 



