NATURAL HISTORY SOCIETY OF GLASGOW. 21 



a swelling out of several joints, and a lateral concave depression 

 with a centre perforation, as in Poteriocrinites crassus."* One 

 very strange figure of Miller's may be referred to here — where a 

 section of a portion of a column is shown with an exudation pro- 

 ceeding from the central canal and collecting on the exterior of the 

 stem as a rounded encrusting mass.f Although not strictly analogous 

 to the swellings at present under consideration, it is probable that 

 it may bear some relation to them, and will be considered later on. 

 Miller describes it in these words: "A calcareous secretion has 

 sometimes exuded on this part, surrounded the column, and con- 

 cealed its articulation, forming an inorganic investing mass, as 

 appears on examining transverse fractures. This exudation some- 

 times swells out into large knobs."! 



Finally, Miller reproduces Yon Schlotheim's figure of the swollen 

 stem of Encrinites mespiliformis.% 



1823. — Von Schlotheim's addition to his previously quoted work 

 contains another figure of a swollen stem of Encrinites mes- 

 2)iliformis,\\ and he reproduces Miller's figure of the perforated 

 and enlarged stem of Poteriocrinus crassus.^l 



1843. — The Messrs. Austin, in describing the stem of Poteriocrinus 

 crassus,* % made the following remarks on the subject : — "Miller was 

 the first to observe the injuries which the columns of this species 

 so frequently suffered. The effect of most of these mishaps, as 

 presented to our notice, is a gradual swelling out into an unsightly 

 protuberance of several consecutive joints, with a considerable 

 concavity on one side. This concavity has evidently been produced 

 by the violent extraction or severance of an auxiliary side-arm 

 from the column, and the Crinoid, in its endeavours to repair the 

 injury and strengthen the wounded part, has, by a rapid and more 

 profuse secretion of calcareous matter, enlarged the joints above and 

 below the severed member, and at the same time closed in the orifice 

 which communicated with the columnar canal." A similar figure ff 

 to that of Miller is given by these authors, and also a smaller one 1 J 

 showing much the same effects. The statement that Miller was 

 the first to observe such injuries requires modification, because it is 

 probable that Ure's figure represents a specimen of Poteriocrinus 



* P. 96. t F. 26. X p. 97. § Plate facing p. 114, f. 17. 



II Nachtracje zur Petrefactenkunde, abth. 2, 1823, t. 23, f. 3d. 

 ^ PjIiL, t. 25, f. 2d. ** Mm. Recent and Foss. Crinoidea, 1843, p. 72. 



ttT. 8. f. h. XX Ibid., f. /. 



