316 THE INHABITANTS OF THE SEA. 



more information about the Brachiopods than an examination 

 of the finest collection of the living species. In each of the 

 above excursions a different set of forms would be collected, for 

 many of the palasozoic genera have altogether disappeared when 

 we rise among the secondary rocks, and in the latter we find 

 forms which closely remind us of existing species, but which, 

 though very near, are yet unquestionably distinct. In forma* 

 tions of all epochs, a few generic types are common, and the 

 Lingulse of the earliest sedimentary formations, presenting 

 traces of organic life, strikingly remind us of the species of 

 that curious group living in exotic seas at the present day." 



At the lower extremity of the great series of molluscous 

 animals we find the Polyzoa (Bryozoa, or Sea-Mosses) and 

 Tunicata. The former, which comprise the Sea-Mats (Flustrae, 

 Escharae), the Sea-Scurfs (Lepralise), the Eetepores, the Cellu- 

 lariae, and several other families, were formerly reckoned among 

 the polyps, whom they greatly resemble in appearance and mode 

 of life, but far surpass by the complexity of their internal or- 

 ganisation. The Sea-Mats are among the commonest objects 

 which the tide casts out upon our shores, for you will hardly ever 

 walk upon the strand without finding their blanched skeletons 

 among the relics of the retiring flood. 

 Their flat leaf-like forms might easily 

 cause them to be mistaken for dried sea- 

 weeds, but a pocket-lens suffices to show 

 that they are built up of innumerable 

 little oblong cells, placed back to back 

 like those of a honey-comb, and each 

 crowned by four stout spines, which give 

 their surface a peculiarly harsh feel 

 when the finger is passed over it from the apex to the base. 

 " The individual cells," says Mr. Grosse, " axe shaped like a 

 child's cradle, and if you will please to suppose some twenty 

 thousand cradles stuck side to side in one plane, and then 

 turned over, and twenty thousand more stuck on to these bottom 

 to bottom, you will have an idea of the framework of a flustra. 

 And do not think the number outrageous, for it is but an ordi- 

 nary average. I count in an area of half an inch square sixty 



