250 DR. r. A. BATHER OX TRIASSIC [vol. Ixxill, 



and showing the clear impression of one joint-face. This, which 

 is beheved to represent the adult stage, is fixed on as the holotype. 

 (B) Three smaller separated columnals, visible in rather imperfect 

 imprints, not far from the holotjpe. (C) Two small united 

 columnals, and, at 16 mm. distance from them, the imprint of a 

 small joint-face. These three sets will now be described in order. 



Description of A, the holotype (figs. 3 & 4, p. 248). — 

 C^dindi'ical. 



Length of fragment = 5'8 mm. 



Diameter — 5" 7 mm. 



Height of a columnal, as measiired = 2 mm. Ratio to diameter =0'35. 



Diameter of lumen = circa 0*4 mm. (not more). 



Sides smooth, faintly convex ; suture depressed. 



Suture-lines with large, rounded, w^ell-marked crenellae. 



The joint-face shows a raised area round the*lumen, and outside 

 this about 28 radiating ridges, which tend to be arranged so that 

 about a third start from the central area and fork, while the 

 remaining 9 are intercalated between these pairs. It is this arrange- 

 ment by threes that has suggested the trivial name teniio, a 

 number containing threes. 



Description of Group B (figs, o & Q, p. 248).— The three 

 columnals are all of about equal size, with the following ap- 

 proximate measurements : — 



Diameter =3" 7 mm. 



Height =1 "8 mm. Ratio to diameter =0 "48. 



Diameter of lumens 0*25 mm. 



In the best-preserved joint-face (fig. 5) there are about 22 

 ridges, arranged in pairs with a shorter one intercalated, as in the 

 holotjpe. 



The joint-face of the adjacent imprint (fig. 6) has a smooth and 

 flat central area, at a level slightly below the ridges. This area is 

 larger than in the other cases, so that the ridges are shorter. 

 Their number is estimated at not less than 22, and they appear to 

 lie in five fascicles of 4 or 5, those in each fascicle being parallel 

 to the median line of that fascicle. 



These smaller columnals are ranked with the holot^^pe, as pro- 

 babl}^ belonging to the same species. The characters in which 

 they differ from the holotype are, on the whole, those of youth. 

 With this the relatively greater lieight of the columnals is con- 

 sistent, though perhaps rather more than might have been expected 

 on that interpretation. I have previously suggested (1909, ]). 9) 

 that the pentamerous fasciculation of the ridges is a frequent, 

 possibly universal, characteristic of youth in the genus Encrimis. 

 It may, however, be manifested in certain regions of the stem and 

 absent from others. In some species the character passes into the 

 adult stage, and in genera of later origin becomes a normal feature 

 (1909, p.' 249). See p. 2-51, under ' llclations.' 



