556 ON THE STRUCTURE AND HABITS 



24. Thick bed of Chinch clay ; x Ammonites, Nautili, and 



Belemnites occur in this bed. 



25. Ferruginous gravel and sand bed, — intervenes between 



the two beds of clay, with nodules of iron Pyrites. 



26. Thick bed of Blue clay-shale, an excellent clay, when 



ground, for tiles and floor-bricks. In this bed are three 

 seams of rubbly ironstone- clay, which dip towards the 

 east, from three to four inches in thickness ; — the second 

 seam is two feet below the first, and the third seam be- 

 tween three and four feet below the second. Fossilized 

 oysters, muscles, and periwinkles are found in this bed. 

 This clay bed is of great thickness, and declines with the 

 slope of the hill ; it dips beneath the sand bed of the ri- 

 ver, and rises again as we ascend Cross o' Cliff hill. 

 The minerals and fossils of the various beds have been 



carefully selected for the Museum of the Lincoln Mechanics' 



Institution. 



Art. VIII. — On the Structure and Habits of the Physalia (ofCuvier) 

 or Portuguese Man- of- War ; Holothuria Physalis, of Linnmus. — 

 By Jonathan Couch, Esq., F.L.S. 



I have not been able to find in any book to which I have ac- 

 cess, such an account of the Physalia as affords an insight 

 into its manner of existence, or adequately represents its pe- 

 culiarities of form or structure. The former, indeed, may be 

 regarded as very simple, as is the case with the greater part 

 of animals which are low in the scale of organization. But 

 wherein they are deficient in extent of endowment, they obtain 

 compensation in the precision of that one function with which 

 their existence is identified ; and in this respect our judgment 

 in regard to some of the obscure or ill-understood functions 

 of the organs of higher animals, may be informed and cor- 

 rected by what is more clearly — because more singly — seen 

 in the actions of these creatures. 



In the days of Pennant the Physalia had not been recog- 

 nized in the British seas. Yet it is not of rare occurrence, 

 and sometimes appears in considerable numbers, keeping in a 

 loose arrangement of companies, floating buoyantly on the 

 surface, and carried wherever the wind and tide are disposed 

 to bear them. 



1 In the descent of the Steep Hill, the great thoroughfare of Lincoln, the 

 clay is indurated, and cannot be made plastic. This clay-shale is from 60 

 to 90 feet in thickness, and must he bored through into the heart of a rocky 

 crust lying below, before water can be obtained. Water can only be ob- 

 tained above and below this indurated clay. 



