John Rofe — On the Swellings on Crinoidal Columns. 351 



probable that it has often been " top dressed," a process which would 

 quickly add to the depth of the soil. It should, however, be men- 

 tioned, that some years since, a field, in the north part of the county 

 Tipperary, was broken up, that had a soil fourteen inches deep, and 

 this field a man, seventy years old, knew to be exactly 110 years 

 in grass. As the average depth of soil, in this part of that county, is 

 from ten to twelve inches in depth, it would leave about 2-5 inches 

 of soil to grow in the century, which is very similar to the results 

 found near Caerleon. 



V. — Note on the Cause and Nature of the Enlaegement on 

 SOME Ckinoidal Columns. 



By John Eofe, F.G.S. 



AMONG a great number of specimens of Crinoidea from the Moun- 

 tain Limestone collected by me during several years past, 

 there are many parts of columns which shew an enlargement of the 

 diameter or bulging similar to that described by Miller as repre- 

 senting " the remedial effect of calcareous secretion in repairing an 

 injury of the joints of the stem," and some few portions have 

 occurred having the apjDearance of a small column rising from the 

 centre of a larger one as shewn in Woodcut fig. 1. 



These last, for some time, were a puzzle not only to myself but to 

 several friends better able to give an opinion on the subject. The 

 small column a seems to be growing from the centre of the larger one 

 without any appearance of a head or of side arms, and without any 

 apparent cause; but further examination of a large number of 

 specimens, an accidental fracture of one of them, and the subsequent 

 dissection of others, suggest an elucidation of this difficulty, and of 

 the cause and nature of these enlargements generally, and at the same 

 time give a clue to the process of the growth of these Zoophytes. 



The column of a Crinoid appears to have been not unfrequently 

 used as a place of attachment for Corals, Brj^ozoa, or Serpulae. 

 Phillips (Geol. of Yorhs., vol. ii, pi. 1, fig. 61) figures the Calamopora 

 parasitica on a stem, and MM. Edwards and Haime (Monographs 

 Pal. Sac.) giving it M'Coy's designation Favosites, also figure and 

 describe it as usually adhering to the stem of an Encrinite. Another 

 Coral, with which this note is more particularly connected, is de- 

 scribed b}'' McCoy as Jania crassa, and subsequently as Cladoclioniis 

 crassus, and he states that " the mode of attachment of the young is 

 most usually by the early branches growing in a circle round a 

 Crinoidal stem." It is over and around the coral thus attached to 

 the Crinoidal column that the enlargement above alluded to is very 

 frequently formed. The coral having fixed itself to and surrounded 

 the column prevents its further natural growth laterally ; but the 

 zoophyte when enlarging its column, which it evidently eff"ected by 

 secreting and depositing fresh shelly matter on the outside, encloses 

 the body or cup of the coral with the column, and by so much 

 increases the size. Certainly in most cases, and probably in all, the 



