Mr. J. Alder on new British Zoophytes. 441 



Laomedea acuminata, n. sp. PI. XVI. figs. 5, 6, 7, 8. 



Polypary minute, scarcely branched ; with a slender, annulated 

 stem ; cells thin, membranous, finely striated longitudinally, 

 elongate-ovate or pod-shaped, squared below, and tapering to 

 a fine point above ; margin slightly crenulated. Polype reach- 

 ing, when extended, to two or three times the length of the 

 cell, with about twenty muricated tentacles, united by a web 

 at the base. 



Height j'^j in. 



On an old shell of Fusus antiquus from deep water, CuUercoats. 



This is an extremely curious and interesting species, which 

 one would scarcely think of referring to the genus Laomedea, 

 were it not for its near alliance to the L. lacerata. The stem 

 rises from a creeping fibre, and is generally more or less annu- 

 lated throughout, the annulations becoming fainter, or entirely 

 disappearing towards the cell. In most of the specimens ob- 

 served, the stem bore only a single polype, but in two or three 

 instances a branch, bearing a second polype, was seen proceed- 

 ing from it. The cells are extremely elastic and membranous, 

 changing form with the polype, and scarcely to be distinguished 

 from it when alive, excepting at the apex when the animal is 

 withdrawn. The polype, when extended, stretches far beyond 

 the cell, the latter adhering closely to it and becoming cylin- 

 drical. The whole animal is very extensile, and frequently 

 changes its form. The tentacles sometimes appear short and 

 stout, and at other times they are extended into long and slender 

 threads, as in the freshwater Hydra, to which the animal then 

 bears considerable resemblance. The tentacles are united by a 

 web for about one-sixth of their length ; a circumstance I have 

 not observed in any other species. The margin of the cell 

 appears to be crenulated, and not divided into deep segments, as 

 in L. lacerata. This character, however, is difficult to ascertain. 

 I have watched the opening of the cell several times when the 

 polype was emerging from it, without being able to detect the 

 exact form of the margin, which is extremely thin and mem- 

 branous. 



EXPLANATION OF PLATE XVI. 



Figs. 1, 2. Laomedea neglecta, natural size and magnified. 



Fig. 3. A cell of Laomedea gelatinosa, Pallas. 



Fig. 4. Two cells of Laomedea longissima, Pallas. 



Fig. 5. Laomedea acuminata, natural size. 



Figs. 6, 7. The same highly magnified, with the polype in different states 



of expansion. 

 Fig. 8. The same with the polype withdrawn. 



k 



