igoS. ' . 171 



DUBLIN MARINE BIOLOGY COMMITTEE. 

 A NEW IRISH GEPHYREAN. 



BY ROWLAND SOUTHERN, B.SC. 



[Pirate 9.] 



In the 5'ear 1862 Keferstein^ gave a preliminary description 

 of a new species of Gephyrean, PJiascolosoina mhudiun, which 

 he had found at St. Vaast, on the coast of Normandy. In the 

 following year he figured the species adequately-, and supple- 

 mented his previous description. Keferstein recognised the 

 characters which distinguished this new species from other 

 members of the genus Piiascolosoma, and in 1865 he created 

 the new genus Petalostoma for its reception^. The species 

 was also found by Selenka at St. Malo. Its only British 

 record is from Plymouth^ where it is said to be " common in 

 crevices of shale." 



In April, 1907, a single specimen was dredged froui several 

 fathoms in Dalkey Sound. In June of this year I found 

 numerous examples under stones near the bathing place at 

 Sandj^cove, Kingstown, Co. Dublin. 



This species is one of the smallest of the Gephyrea. When 

 contracted it is 5-7 mm. long. It expands to a length of 

 10-14 mm. The retractile proboscis is longer than the 

 bod3^ The general anatomy of the body, and the structure 

 of the tentacles are well shown in Keferstein's figures. The 

 body is cylindrical in shape (Plate 9, figs, i, 2), sharpl}^ conical 

 behind, and tapering gradually in front. It is somewhat 

 more active in its movements than is usual among the 

 Gephyrea. The proboscis is being constantly protruded and 

 retracted, so that the structure of the tentacles at the tip is 



"^ Nachnchten d.K. GeselL d. Wissenschaften zu GiHtingen, 1862, p. 66. 

 ' Zeitschrift f. wiss. Zoologie, Bd. xii., 1863, p. 40, Ta/>. iii.,/^5-. 7-10. 

 3 ZeiL f. zviss. Zoologie, Bd. xv., 1865, p. 438. 

 ^ founjal Marine Biol. Assoc, vol. vii., 1904, p. 233. 



