Royal Society. 209 



a fringe of cilia round each, designed to produce currents of water 

 over the extremities of the caeca. 



The resemblance which these caecal prolongations of the sinus- 

 system into the shell of the Terehratula bear to the vascular pro- 

 longations of the sinus-system into the test of certain Ascidians, is 

 not without its parallel in another group, which (as pointed out by 

 Mr. Hancock, Ann. of Nat. Hist. vol. v. p. 198) is intimately re- 

 lated to that of Brachio])oda, — namely, the Bryozoa. The stony 

 walls of the ' cells ' which invest the soft bodies of many species of 

 Eschara, Lepralia, &c., are marked, like the shells of Terebratulae, 

 with punctations, which are really the orifices of short passages ex- 

 tending into them from their internal cavity, as sections of these 

 structures demonstrate. These passages I have found to be occupied 

 by prolongations of the visceral sac, which is the only representative 

 of a circulating system among these animals ; and they thus convey 

 the nutrient fluid which this contains, into the substance of the 

 framework formed by the calcified tunics of these animals. 



I need not here enlarge upon the additional value which these 

 structural and physiological considerations afford, to the character oi 

 " perforation " or " non-perforation " in the shells of Brachiopoda. 

 7'he importance of this character in systematic arrangement will 

 plainly appear, I think, from the details which I have published in 

 the Introduction to Mr. Davidson's Monograph already referred to. 



March 30, 1854.— Thomas Bell. Esq., V.P., in the Chair. 



" On the Structure and Affinities of Triyonocarpon (a fossil fruit 

 of the Coal-measures).'* By Joseph D. Hooker, M.D., F.R.S. 



Having been for some time engaged in examining the structure 

 and affinities of some fossil fruits of the coal formation, included 

 under the name Triyonocarpon, and the progress which I am enabled 

 to make being extremely slow (owing to the difficulty of procuring 

 good specimens), I am induced to lay before the Royal Society such 

 results as I have arrived at, for publication in their Proceedings (if 

 thought worthy of that honour). The details and illustrations of 

 the subject will, when complete, be offered to the Geological Society 

 of London. 



My attention has for many years been directed to the genus Tri- 

 yonocarpon ; as, from the period of my earliest acquaintance with 

 the flora of the carboniferous epoch, I have felt assured, that bota- 

 nically, this was the most interesting and important fossil which it 

 contained in any great abundance, and that until the affinities of this 

 were determined, the real nature of the flora in question could never 

 be regarded as even approximately ascertained. 



In the first place, Triyonocarpon is so abundant throughout the 

 coal-measures, that in certain localities some species may be pro- 

 cured by the bushel ; nor is there any part of the formation in which 

 they do not occur, except the underclays and limestone. The sand- 

 stone, ironstones, shales, and coal itself, all contain them. 



Secondly. The symmetry in form and size which many of them 

 Ann. S^ Mag. N. Hist. Ser. 2. Vol.\\\. 14 



