66 PROCEEDINGS OF THE 



most zealously over the same spot, "nitli no better success.* These 

 repeated failures, where vre had at first been so successful, would 

 appear to warrant the inference that this species may migrate in 

 shoals, and live in societies, one of which had obviously been met 

 with when they came up clinging iu such numbers to the netting. 

 Their occurrence on the Laminaria, on which the young Penfacrinus 

 may be sought for, would seem further to point out the purpose 

 for which this migration takes place. 



A haul through the mud of Eothesav Bay, however disasrreeable 

 the process of examining it be, will repay the trouble. Such a 

 habitat, from its unattractive nature, conceals many objects which 

 are accounted rare, but which, on ordinary ground, would not 

 long escape notice. 



Tuhularia indirisa, with its beautiful scarlet polypite and tenta- 

 cles, will be found in considerable abundance. Sometimes the 

 little heads, having dropped off, will be seen lying curled up, so 

 as at first sight to resemble some small £oIid. 



Ophiura texturata and 0. aUAda also occur, but the most char- 

 acteristic and most abundant star-fish is 0. fiUformis — the thread- 

 rayed star. It is found only in the mud, and is common on such 

 ground in the Gareloch, Gourock, Largs, and elsewhere in the 

 Firth. Wlien brought up, their long delicate rays will be seen 

 moving through the mud, from which it is hopeless to extricate 

 them, as they break into fragments on any attempt to pull them 

 out; but if it is allowed to stand for some time in a bucket, 

 then the most brittle of brittle-stars will all come to the surface, 

 and may be lifted up very entire. An instantaneous plunge into 

 a cold fresh bath is the only way to keep them so. 



"We were not so fortunate, in one or two trials, as to find Bryssus 

 lyrifer, the Fiddle Heart-urchin, which was first described by 

 Edward Forbes, from specimens found in this district. We 

 obtained it, however, in the mud ofi" Ashton, Gourock: and shortly 

 after, in dredging ^vith Messrs Eobertson and Keddie in the Bay 

 of Largs, several were brought up, and it would seem there to be 

 very abundant. This species is the only British Heart-urchin 

 inhabiting mud, in wliich it probably lies concealed, like the 

 common Heart-urchin, Amphidotus cordatus, in our sandy bays. 



* Since that, Mr Eobertson has tried it several times, but not till last year, 

 1 867, did the Comatvlas re-appear, when they were abundant, aa also was the 

 Peritacrinus, one frond being thickly covered with them. 



