402 Dr. F. A. IJatlicr un Briti.i/i Fosull Crinoids : 



The Diameter varies from 3 mm. (57542 e) to 6*4 mm. 

 (57541) ; ill general it is about two-thirds that of B. di- 

 ll actylus. 



The Side-Faces in all specimens appear smooth, but the 

 state of preservation is such that the original surface has 

 often been destroyed or coated over, so that minute granules 

 may have occurred in some stems. The surface is also 

 plane or equable as a rule, but various specimens show slight 

 swellings either about the equator of the colnmnal (cf. Forbes, 

 fig. 9) or near each margin ; occasionally tiiere are irregu- 

 larities suggestive of the granules that border the radii in 

 sojne specimens of B. didactylus. There are, however, no 

 such marked ridgings as occur in that species. Some 

 specimens have radial pores well marked (Sowerby, fig. 3 a ; 

 Forbes, fig. 8), others appear to be entirely without them ; 

 but there are intervening gradations. 



The Number of lutcrnodals varies from 14 in 57541, 

 which is from a proximal region (vide infra), to over 29 in 

 the two smooth specimens under 57551. 



The internodals of smooth forms are equal in height, but 

 the syzygial ossicles are usually lower in adult stages. The 

 following are some measurements in millimetres : — 



57542 e. 57542 c. E 5638 a. 57543 c. 57540. 57843 <Z. 57543 6. 

 Diameter .... 

 Ileiibt of iuter- 



iiodal 



lleiglit of epi- 



zygal 15 



Alternation in Height of internodals is more frequent in 

 the quinqutlobate or substellate fragments, which no doubt 

 come from more proximal regions of the stem. It is 

 usually accompanied by a slight increase in the diameter of 

 the ossicle. In 57542 a, with mean diameter about 35 mm., 

 internodals of 1*2 mm. are interspersed with others of 

 I'O mm. in height; the epizygal is 1'35 ; the hypozygal 

 10 mm. In 57542 Z», with diameter 4*2 mm.^ the inter- 

 nodals are arranged thus : 



1-4 / 1-8 / 1-4 / 2-1 / 1-4 / 1*4 / 1-8 / 1-4 / 1-8 / 



In 57543 a, with diameter 5*0 mm., the height of inter- 

 nodals varies between 2*0 and 1*7, the epizygal being 

 1"8 mm. In 57541, with diameter 6*1 mm., and well- 

 marked rounded stellate section, there are two epizygals 

 (Order I), each about 1'5 mm. high ; between these are 

 tiiree internodals of about 1*3 mm. (Order II), separated 

 from each other and from the epizygals by 3 internodals of 



