276 Mr. P. H. Gosse on Sarcodictyon catenata. 



the tip ; each segment of the abdomen below has on the sides 

 a small obscure whitish spot. 



Length 11 lines. 



Hab. S. America ? (H. G. Harrington, Esq.) (Coll. Brit. M us.) 



XXIX. — On Sarcodictyon catenata (Forbes). 

 By P. H. Gosse, F.R.S. 



[With a Plate.] 



The possession of a specimen of Sarcodictyon catenata in the 

 highest health and vigour enables me to add a few particulars 

 to what is known of its economy, and to give a figure of its 

 appearance. I should premise that I have not by me the original 

 account of the animal as published by the late Edward Forbes, 

 but only the citation of it by Dr. Johnston in his l British Zoo- 

 phytes/ ed. 2* p. 179, and the figures in plate 33. figs. 4-7, 

 which, he states, were copied from Forbes' s drawings. 



My specimen was obtained on the 8th instant, at Ilsam, in 

 this neighbourhood. Having chiselled off several pieces of the 

 perpendicular sides of a sub-cavemous rock at extreme low- 

 water, spring-tide, and plunged them, when brought home, into 

 sea-water, my little son found, while examining them the next 

 morning, several expanded polypes on one of the fragments, 

 which seemed to him new, and to which he called my attention. 

 On examination, I found that they belonged to this interesting 

 species. 



The creeping band is about half an inch in length and half a 

 line in diameter, running in an irregularly sinuated direction. 

 Within this space are five polypes, and there are three or four 

 more scattered on the stone, close to the band, but whose con- 

 nexion with it I cannot trace, nor with each other : they appear 

 isolated. The colour of the band, which has a fibrous texture, 

 is pellucid red; and that of the polypes, when contracted, is 

 opake pale red. Not one of Forbes's figures (in Johnston) 

 bears more than the most remote and rude resemblance to what 

 I see, with the exception of the right-hand polype in fig. 5 (op. 

 cit.) } which is a tolerable representation of the contracted con- 

 dition ; too conical, however. 



The individual polypes, when in this state, bear a very close 

 resemblance to a minute Sagartia: they are invested with a 

 pellucid epidermis, which is thrown by contraction into annular 

 folds. These folds are seen encircling the lower part of the 

 column alone when the animal is fully extended (see PI. IX. fig. a). 

 Expansion takes place in the ordinary mode, the animal gradu- 

 ally taking a columnar form, and at length attaining a height 



