442 H. L. Hawkins — Tubercnlution of Holectypoida. 



the surrounding rock. Wyville Thomson l considers these pseudo- 

 palmetto stems to have been formed on the floor of caves by the 

 dropping of water charged with calcic material in solution. But these 

 pseudo-palmetto 'fossils' are mostly hollow, while stalagmites are 

 not. The pseudo-palmetto fossil figured is from the Walsingham 

 rock on the east side of Hungry Bay (PI. XXII, Fig. 2). 



In conclusion, I would thank those in Bermuda whose names have 

 been mentioned in the course of this paper, also Dr. Henry Woodward 

 for editorial advice, Mr. Bullen Newton for access to Major Peile's 

 collection at the British Museum (Nat. Hist.), Mr. Holland for 

 examining and reporting on the Foraminifera, and Miss G. M. 

 Woodward for preparing the illustrations. 



EXPLANATION OF PLATES. 

 Plate XXI. 

 Fig. 1. Deep cut (' Khyber Pass '), Warwick parish, from a view published in 

 Bermuda. 

 ,, 2. Pinnacle in seolian rock, St. George's, north shore. 

 ,, 3. Pinnacle in process of formation by eeolian agency, Bailey Bay, north 

 shore. 



Plate XXII. 

 ,, 1. ' Pot-holes ' in process of formation, St. David's Head. 

 ,,2. ' Pseudo-palmetto stump,' cliff east side of Hungry Bay. 

 ,, 3. Beticulated, honeycombed, hard limestone, showing effect of sea spray, 

 rain, and air on exposed rock. In the centre of the rock is a pocket 

 of soft shell-sandstone. Both the hard and the soft rock contain 

 innumerable land shells of P. Bermudensis, var. zonatus, Verrill, 

 and belong to the same series of Paget rocks. At ' x ' a fine Livona 

 pica was dug out by Mr. E. Morton Ingraham, of New Britain, 

 Conn., U.S.A. 



Plate XXIII. 

 ,, 1. Grey rock from the ' Khyber Pass ', Warwick, Bermuda. x 8'5. 

 ,, 2. Phosphorite with Staffelite (Guano rock), Manhattan Shoal, near 

 Paget Island, St. George's, Bermuda, x 10. 



II. — On the Tuberculation of the Holectypoida. 



By Hebbert L. Hawkins, M.Sc, F.G.S., Lecturer in Geology, University 

 College, Reading. 



I. INTRODUCTION. 



ONE of the most obvious contrasts between the Regular and 

 Irregular Echinoids is in the character of their radioles, and 

 of the tubercles on which the radioles are supported. Among 

 the Begulares the size of the radioles is usually in inverse proportion 

 to the number which rest on an individual plate of the test; and, 

 to some extent, the same generalization applies to the Irregulares. 

 There is, however, a differentiation of the radioles among the 

 more typical Irregular groups, which results in a corresponding 

 irregularity in size and disposition of the tubercles. Generally 

 speaking, the radioles of the Regulars are stout and few, while those 

 of the Irregulars are slender and numerous. While, in an Echinw, 

 the largest and strongest of the radioles are ambital, or even superior 



1 Atlantic, vol. i, p. 330. 



